The zynq XC7Z010 FPGA SoC IC can be had for less than $20, but routing a board with SDRAM is a major effort; there have been some system-on-module boards but they all either lack SDRAM or are really expensive. I'm looking for something on the order of $50 with at least 256MByte SDRAM that I can easily integrate into a system; does such a product exist or am I looking at designing my own?