Josh,
I did a little searching on Newegg.com and found video cards that support 2560x1600 resolution starting at $95.00. Of course they up quite a bit higher than that, but there are several options under $200.
Here is the NEWEGG link for the page I found. These are PCI Express X16 cards. There are 14 choices. You should be able to get an idea for here.