It all depends on where the person lives. For me FPGA's are a profitable option for mining bitcoins because of the extremely high power bills in Australia (about 0.25 AUD per kilowatt). On average half of the coins generated by my GPU miners go back into power costs. Doesn't mean I have taken them down however since coming into winter the heat they generate more then makes up for it. But in the long term FPGA's with their lower power draw means that I can keep more of the coins that I make and while they do have a higher upfront cost they pay themselves off faster. But use the calculators and see what is best for you.