Are you open to used putters, or does it have to be new? At the stores near where I live, there are usually a healthy selection of pre-owned putters, some of them are in good or even great shape. I found my dad a center shafted TM Rossa Ghost for $79.99, in very good shape!
I also picked up an Odyssey Black Series #7 (also in very good shape) for $79.99.
IF you're really only looking for new, Cleveland has a low priced series of putters out there. They don't use the 303 stainless ala Scotty Cameron or the other milled shops, but they're of a good quality (17-4 stainless) and reasonably priced ($99.00 new, I think).
Finding "the one" is more of a personal issue, of course. Good luck!