Houston signed Omer Asik with a so-called "poison Pill" to ensure that the Bulls would not match. His contract is structured like this:
For cap purposes his salary is$8,374,646 per season.
Asik has been rumored to be on the block. At this point the team trading for him would be assuming $20,123,938 in salary for 2 years, averaging just over $10m per year. Houston will have received one year of his services for only $5m.
Furthermore Asik's trade value would diminish over time. After 13-14 he would then be due $14.898,938 for one year.
If the Rockets wish to trade him, I would think the Celtics, like other teams, should be interested.