GPU has average MH/watt and good MH/$.  FPGA has good MH/watt but bad MH/$.  This is an attempt to improve the MH/$ by making the hardware cheaper.

They've succeeded making the MH/$ better but still not as good as GPU.  Currently GPU mining is break-even due to power cost and FPGA mining is profitable.  It will take a while to pay off the $50/175MH hardware but it will eventually happen unless mining profitability falls lower.

It is an interesting hobby project if you want to try it.