- In the NBA the full contracts of players are guaranteed, unlike the NFL. So the only way for them to come off your pay roll, and thus come off your salary cap, is for them to expire. (There are some exceptions where you can waive a player earlier and pay fees but just ignore those for now).
- The NBA has a soft salary cap, unlike the hard cap in the NFL, which means teams can spend over the salary cap limit by using a list of different cap exceptions. I would say most teams go over the salary cap most years.
- If a team is over the salary cap, if they want to trade for a player, they have to make sure the player(s) they ship out have a similar salary that year to the one(s) they get back in return. Specifically, the total salary they receive can be no greater than 125% of the total salary they give away.
Okafor's deal is scheduled to expire next season, and he's scheduled to make 14.5 million dollars in salary next year. That's like 25% of a team's total salary cap, so it's a big contract. That means roughly 25% of a team's cap becomes free that offseason when his deal expires. So teams trying to get under the cap to make FA moves or save money or whatever, would really want to trade for Okafor. It's an opportunity to shed a ton of salary in one shot.
And to top it off, Okafor is pretty good. Usually when you trade for an expiring contract, you have to just eat that money because the guy sucks or is injured. Okafor can actually help a team win at a crucial position for the duration of his contract.
It's also worth pointing out that we could use Okafor ourselves and we could use the cap savings next summer too because we'll be negotiating an extension for Wall. So it'd only be worth our while to trade Okafor if we actually got something good in return. And remember, if the teams in the trade are over the cap, the salaries have to be within 125% of each other. So we'd be taking back ~13-15 million dollars in salary back ourselves. That's a star player type contract. So that could either be a ton of money in bad contracts or a ton of money in a disgruntled star or who knows what teams would offer.