£30-50 for a cheapish one, they need phantom power from a mixing desk or pre amp unless you get a usb one around £50
http://www.google.co.uk/products?hl=en&q=usb+studio+condenser&scoring=p

I dont think it really matters though, its only vocals and bearing in mind the low quality mp3 rate it will end up as and the speaker systems it will be played through as long as it is audible differences in mic quality and gonna be noticable. My housemate does a podcast using a condensor and one day it broke so he used the tiny mini-jack mic from my ultra budget electronic dictaphone, sonded pretty much the same.