I just bought a pentax-m SMC 50mm f1.4 off ebay for about $150 which is a bit high but its still way cheaper than the canon 50 1.4. I still haven't gotten it in the mail yet, but from everything I've read in reviews and on ns it blows the canon out of the water.
You could definitely get the lens and adapter ring for well under 200$ including shipping and maybe even under $150.