Houston, after failing to sway Dwight Howard's mind about coming to an organization that functions well instead of the Billy King led Nets and dealing Dalembert for draft picks, has attempted to fill out the center position with Chicago's back-up, Omer Asik. Based on the Gilbert Arenas provision, Houston is offering him $5 million for each of the first two years and then $15.1 million the third and final year, but it only counts for about $8 million each year against their cap. Chicago, however, if they were to match wouldn't get to use the $8 million number, but instead would have the $15 million count against their cap in the third year. Houston structured the deal precisely so the Bulls wouldn't match because of the problems that would occur trying to fit that enormous third year with their other salaries.
The question remains, however, isn't $25 million too much for a back-up center who averaged 3.1 points per game and 5.3 rebounds. The Rockets are one of the most stat-inclined teams in the league, and the story behind Asik is his monstrous impact defensively. Consider that the Bulls are already one of the best defensive teams and he's backing up one of the better centers with respect to that end of the court. Regardless, the Bulls play even better defense when he's on the court, and although this is due to their defensive second unit that also consists of uber-defensive player Taj Gibson when you adjust for who's on the court he still has a large impact. Regularized +/- stats, for instance, give him one of the best defensive scores.
Notice that offensive hasn't been mentioned yet, and that's because he's almost as bad there as he is on defense. His fingers apparently melted together and as such he's unable to handle the ball without turning it over to the other team, and he rarely shoots from even three feet away from the basket and during the course of his two years in the league he's only taken eight shots from 10 feet or further. Despite his offensive limitations as a center most of his value is on the defensive end where he's guarding the basket, and as a 25 year-old it's a better investment than, say, Kenyon Martin, who will keep getting worse as he gets older.
There's also a precedent here. A back-up international center in his second year and his mid 20's in the east was offered a huge contract as a restricted free agent from a western conference team. That player was Marcic Gortat, and in 2009 the Dallas Mavericks offered him a 5 year, $34 million dollar contract, which the Magic promptly matched. At the time the Polish center was buried behind Dwight Howard and during the 2008-09 season averaged 3.8 points and 4.6 rebounds. The Magic were able to match the contract, but a year later they traded him to Phoenix for Turkoglu and Jason Richardson (possibly on a dare.) Gortat has quickly become one of the better centers in the league and averaged 15-10.
The situation is similar to Asik's in a few different ways. Not only was he a back-up center, but it was common to hear people say Gortat had a lot of talent but needed an opportunity to play. The same is true for Asik, but not to the same extent because he's more defensively inclined and that inherently gets more press. The general reaction even among people familiar with his advanced defensive stats was surprise at the size of the contract, but upon looking at the situation more closely and what other centers make it's more logical. Remember this when JaVale McGee is given a huge amount of money even though on a terrible team like the Wizards the team played better with him off the court.
One legitimate issue, however, is how he can adjust from a limited bench role to what will likely be a starting one. He doesn't even play more than 15 minutes on Chicago, and back when he was in the Euroleague it didn't eclipse 23 a game. He also fouls nearly twice a game in limited minutes, and using some basic math it would be hard for him to play heavy minutes. Obviously, he'll learn to cut down on his fouls as he gains experience and is pressed into a starting role, but there's still a question of basic conditioning. He would have to play at least 30 minutes with few missed games to justify the contract, and there's no guarantee how well he'll play.
But that's the problem with evaluating basketball moves. There are no perfect solutions; instead it's a set of unsolvable problems and calculated risks, betting that your guess at what the future holds is better than the other team.