not sure they haven't always been fairly accessible? I suppose prices are now dirt cheap vs. 2010/11 where I'd have to pay 300-400 for a mediocre FPGA (I've used digilent for years, prices on there have dropped quite fast in the last two years or so). then again, atmel had an FPGA co-processor for awhile at a relatively cheap price (can't remember the name...probably X28 with some characters), but still not really capable of running a neural network at any appreciable depth.