Haunt the sales- and the thrift stores. I've been slumming for vintage a lot lately, and got a brand new flourescent yellow pearl izumi for a dollar at Sal. Army. Now this was luck, but if you go to thrift stores anyway, check. they're always in the mens dept.
Very rarely, Marshalls has great stuff, also always in the mens dept. Got an amazing winter jacket for $20. These are rare finds, but if you're going anyway, take a look. And then there's ebay...
I have a few $20 Nashbar jerseys I dressed up with iron on butterflys and Grateful Dead bears over the logo. Fun! And Primal is pricey, but worth it. I choose carefully and love every one of them. Have to get the mens 'cause I have broad shoulders and big boobs, then take out the elastic and rehem, but I haven't killed one yet!
Cheapest of all- at Walmart mens dept there are Starter wicking shirts with zippers, essentially jerseys with no back pockets. Needed hemmmimg and more loud iron on toodootsies over the ugly logo, but ten bucks.
Remember, most jerseys wear like iron. The initial outlay is painfull, but they last forever. I suspect my Primals will oulive me.

missliz