$15,000,000 on a player that can barely contribute anymore is a really hard asset to move. Think of how many players a team would have to give up to move that contract: a team would give up 3-4 role players for what? Less salary in the summer?
And any larger contract that someone is willing to move without asking for more assets back would likely be a contract the Raptors
don't want anyway.
Expiring contracts aren't really worth that much. Don't hold your breath on that TPE, either....