It works. Otherwise, Kaervek's Torch wouldn't work at all.
What does Torch have to do with this?
If you paid costs before targets were chosen, then Torch's ability wouldn't happen. You'd put Counterspell on the stack, pay UU for it, then target Torch. Torch would say, "Okay, when you pay your mana, pay an extra 2." You say, "Ha! I already paid! Too late, sucker!"
But that's not the case. You choose targets, then pay costs. Which explains why you can have Wasteland target itself.