Yeah, "Performance" ain't cheap.

Watch the internet for sales, and or used wheels. Or check out "Salvage Yards" like LKQ for smaller, lighter Mercedes wheels.

By the way, the improvement in 1/4 mile times I mentioned were documented in Motor Trend magazine in a comparison road test between an 04 Crossfire automatic, and a 03 SLK320. Even though the SLK weighed more, it was faster, just because or the lighter weight wheels.
At least 16 and 17" tires are usually a lot cheaper to buy than 19", and a good used set of smaller aluminium Mercedes wheels shouldn't cost ya more than 400 or $500 I would think.
Ya might even get lucky and find some that still have some decent tires on them.