I bought March pulleys set for my 340 and I wanna say they were around $325 for my alt, WP, crank, and PS pump. I also bought the face cone covers for the Sanden AC, the WP and the alt. Are you pricing directly from March?
Also, I had a lot of trial and error; had to have my WP pulley custom cut based on the March model. I think it was just over $100 but it was custom for my dual belt drive design. Doubt you would need to go to that extreme.
Check the classifieds, was pretty sure someone was selling a March set for SB.