Using your logic, nearly all buyouts are nonsense. The idea behind them is the team and the player want to separate and they reach an agreement for the player to get something less than the remaining amount on the contract. What the dollar figure comes to is subject to negotiation. So in reality, a buyout between the Sixers and Webber makes obvious sense for both sides. The team doesn't want him and he doesn't want to play for the team.
No, I think this buyout is nonsense. Most buyouts aren't trying to buy out the highest paid player in the league. Waiting until his final contract year and trading his expiring has more value and makes better sense. If I was Webber, I wouldn't accept a buyout for anything less than the total contract value owed me less the vet minimum I could get signing with another team.