Cheapest place I've seen the bilstiens is shox.com....and btw, it should be the last set of shocks you would need to buy, lifetime guarantee. Definatley worth the $$, the quality is just outstanding. Order a set, and you'll see what I mean.
I dont think you are going to find Bilsteins cheaper that the $260-270 range. They are worth saving up for. If you are completely against it, then look into the monroe severe service shocks. There is a long post all about them and prices in this section. Just do a search by the name. I know those are significantly cheaper than the Bils.
If you decide on the Bils, look into getting the firm (sport) 1104/0929 Bilsteins.
The Monroe severe Service Shocks are good. $160 for four at Advance Auto. Need to special order but delivery is like 2 days. Lifetime warranty at Advance Auto. Only a 1 yr warranty at NAPA and some other places. #'s are 550012/550013.
the 1104/0929's are the sport shocks. thats what i run. They're stiffer than the HD's. they made a major difference in my ride and handling. i think they were worth it even though i dont know how the monroe shocks handle. I like my bilsteins a lot though. you wont be disappointed