I haven't kept track, but I've probably spent over $200. I just got Beejive for $16, and I've bought several apps around that price. I've bought a bunch of games and utilities for around $5-10, so yeah, I'm probably around $200-250.
I've bought a few clunkers along the way, but the cost is low enough that I don't mind experimenting. I like seeing all these little "mom and pop" (ok, mostly "pop") developers submit applications. I hope one of these little guys ends up an 800lb gorilla of the industry some day.