Alright, after gluing my brain back together, this deal is still good for the Grizzlies but it makes more sense.
The real deal = "Memphis sent big man Marreese Speights, guard Wayne Ellington, guard Josh Selby and a future first-round draft pick to the Cavs for forward Jon Leuer."
Trash for Leuer is a wash. (I'd rather have Leuer than those three at a cost of $6M, though.)
The first round draft pick is basically a bet by the Grizzlies that they'll remain a playoff team for the rest of this decade. That's a decent bet but it's also somewhat risky. They're a couple injuries away from sliding down and losing a late lottery pick, IMO. So, yeah, that's a risk.
But the big win for the Grizzlies is it looks like they'll be able to keep the rest of their team together.
All in all, an acceptable trade by both sides. The Cavs are basically paying $6M for a chance at a lottery pick ... which isn't a bad gamble. The Grizzlies are shedding three players they didn't need for a decent prospect and the right to keep their team together, while taking the risk of losing a lottery pick down the line. That sounds pretty smart, too.