Same tuna, different price

not realizing she was looking in the wrong place. The real bargains were 2.3 miles away at a Shaw's Supermarket in Medford. The Shaw's and Star are both owned by the same company and their circulars contain the same sale items. But the prices on the sale items in Somerville are significantly higher than they are in Medford. For 12 items on the cover of the circular, the Somerville store was charging more -- a total of $6.51, or 17 percent, for this group of specials.

"I've never noticed that," said a stunned Hoey as she compared the two circulars, noting that in the Somerville circular Spanish clementines were a dollar more a pound, toilet paper a dollar more for a 12-pack, and Oreos 50 cents more for a 15-18 ounce bag.

New England's two largest supermarket chains are perfecting the art of charging whatever the market will bear, distributing to consumers customized weekly circulars with sale prices that often vary dramatically from store to store within a chain depending on the level of competition in the area.

Shoppers interviewed last week at several stores said they weren't aware of the practice, and many said they were surprised by it. The chains don't hide their pricing policies -- their circulars identify the specific store or stores to which they apply -- but they don't publicize them either.

A Globe review of the circulars covering 65 Shaw's and 68 Stop & Shop Supermarkets in eastern Massachusetts for the last week in October found that prices differed by as much as $5.30, or 48 percent, within the Shaw's chain on a marketbasket of eight circular items. Prices differed by as much as $1.51, or 26 percent, within the Stop & Shop chain on three items in the circular. Marketbaskets at each chain are not meant to be compared to each other but to stores within the chain.

Overall, sale prices tended to be the lowest south of Boston, where competition from other supermarkets, Wal-Marts, and warehouse clubs is the most intense. Sale prices were the highest to the west of Boston, in Newton, Waltham, Framingham, Natick, and Westborough.

In the metropolitan area itself, prices were high in Cambridge, Brookline, and Roxbury and relatively low in Dorchester and Hyde Park. To the north and northwest of the city, prices were a mixed bag -- some high, some low.

Nearly every supermarket chain in Massachusetts prices its sale items based on the level of competition it is facing in a particular area or to promote a new store opening. The chief exception is Demoulas Supermarkets of Tewksbury, which, except in rare instances, doesn't vary sale prices from store to store.

Industry officials say pricing differences may be more pronounced now because of fierce competition, particularly on the South Shore, but they say their pricing strategy is no different from what a gas station does when it lowers its prices to match a competitor across the street.

The Medford Shaw's, for example, faces competition from a nearby Stop & Shop, a Johnnie's Foodmaster, and a BJ's Wholesale Club. In Somerville, Shaw's has three stores and faces limited competition. That may change, however, as Stop & Shop is planning to build a store in the old Somerville Lumber location.

"We price competitively in each individual marketplace and the competition in each area can be dramatically different," said Faith Weiner, a spokeswoman for Stop & Shop. She said the chain monitors the prices of competitors on a daily basis.

Terry Donilon, a Shaw's spokesman, said store prices are based on the "competitive landscape at each location." He said the chain is upfront about that in its circulars and online, where circulars for each individual store were recently added.

A chain's circulars all have the same general appearance, carry most of the same items, and have identical prices for most of those items. But on roughly seven to 20 high-profile products the prices often change from store to store within the chain.

Stop & Shop appears to change the prices of fewer items than Shaw's and tends to be more subtle in its approach. In the Globe's survey, 19 Stop & Shop stores were charging $7.38 for the three-item marketbasket, with the chain's remaining 49 supermarkets charging lesser amounts, down to a low of $5.87.

No Stop & Shop market had the lowest sale price on each individual circular item, suggesting the chain was trying to blend high and low sale prices in a calibrated bid to attract customers.

In Brockton, where a new store recently opened, Stop & Shop's supermarkets during the last week in October were offering the chain's lowest prices on a 2-liter bottle of Coca-Cola (59 cents), and a half-gallon of Friendly's Ice Cream ($1.50). But the $3.99 price for a four-pack of Bumble Bee tuna matched the highest sale price offered by the chain.

Shaw's tended to be more aggressive in changing its circular prices, particularly on the front page, but it also had a large percentage of markets charging the highest sale prices. The Globe's survey found 23 Shaw's supermarkets charging $16.39 for the eight-item marketbasket, with the remaining 42 stores charging lesser amounts, down to a low of $11.09.

Eugene Fram, a marketing professor at the Rochester Institute of Technology in New York, said supermarkets use their specials to lure customers into their stores and then attempt to sell them other items with higher profit margins. "They have to balance it off," he said.

While lower prices on specials are probably a good indicator of relatively lower everyday prices, that's not always the case. The Shaw's stores in Salem and Cohasset had identical prices for sale items during the last week in October, but the savings claims in the circulars indicated Cohasset was the more expensive store for nonsale items.

A can of StarKist solid white tuna was on sale for 79 cents at both stores, but the Cohasset circulars indicated the shopper was saving 60 cents at that price while the Salem circular said the shopper was saving only 20 cents. Savings were also greater in Cohasset on steak, chicken, Pepsi, and Edy's Ice Cream, while savings were greater in Salem on Prego Pasta Sauce. Overall, the circulars indicated the regular nonsale prices of the six items would have been $19.34 in Salem and $22.14 in Cohasset.

In interviews at several stores last week, shoppers expressed surprise at the price variations. Hilda Dasilva of Somerville said she had no idea Shaw's circular prices could vary so much between Medford and Somerville. "Maybe I'll start shopping over there now," she said, referring to the Medford store.

Edgar Dworsky, the editor of Consumerworld.org and a close observer of supermarket pricing, said he accidentally discovered circular prices differed from store to store within a chain when he mentioned a good sale price to a friend and the friend reported that the price was different in his circular. Dworsky said the wide variation in circular prices surprised him.

"You'd almost expect the specials to be the same everywhere, but apparently the specials are more special in certain places," he said.

The circulars Shaw's sends to customer homes are the same ones available in its stores in that area. The chain also just started posting its circulars on its website, allowing consumers to search by zip code.

Stop & Shop, by contrast, delivers to consumer homes a 10-page, customized circular for their local store. In stores, however, the chain makes available only a generic four-page circular that contains none of the customized specials.

Quincy residents, for example, received circulars at home recently advertising a four-pack of Bumble Bee tuna for $2.99. But the in-store circular listed the price at $3.99. The $2.99 price rang up when the item was purchased, but the consumer walking in off the street and looking at the in-store circular would have no way of knowing the item was selling for a dollar less without checking the shelf. Weiner at Stop & Shop said the in-store circular was not designed to keep walk-in customers in the dark, but instead to alert them to specials while keeping the chain's overall printing costs down. "Obviously, we want them to come into the store, get great deals, and keep coming back," she said.

Bruce Mohl can be reached at mohl@globe.com. Globe correspondent Bill Dedman contributed to this story.