I lucked out.
I bought a set of Dunlop Sport M3's off of craigslist, $100. The guy even dropped them off to my work. I swear they are as new.
I also scored OZ Superleggeras which would normally cost $1500+ with only 2000 miles on them and are mint, $375 from a BMW tech friend.
So scour the forums and CL, there are deals to be had.
'98 M Roadster S/C @11-16ps
'06 Saab 9-5 wagon 5mt Aero+ Tuned