My understanding of buyouts and the tax is that team's tax figure is based on their payroll at the end of the season, so midseason trades that save a few hundred thou, like what N'Owlins did, help at the end. If a team just waives a player with a guaranteed deal, the salary stays on their books, so the buyout is preferable to the wave.
For buyouts, a $10 million player gets bought out and the team saves whatever the player would make playing elsewhere, say the league minimum of $1 million (or prorated, whatever). The team's number for tax purposes is $9 mil instead of 10, saving them that much in taxes in addition to the actual salary saved.
In Ray's case, though, teams may want to keep him for summertime sign-and-trades, so we shouldn't presume teams will want to buy him out. Our other expirings would probably be strong buyout candidates.
Keep in mind teams still need to carry a minimum of 13 players, too, so they can't buy out everyone they don't want.