I've been surfing FPGA sites today.

Turns out you can develop your prototype adapter on an FPGA, and then make a "write once" copy of it on a much cheaper CPLD (programmable logic device). Exact same code goes in. So that makes the end product a load cheaper than the prototype, as far as I can tell, especially if you can squirt the CPLDs at home.

NB somewhere on that site there's a mention that their FPGAs are PCI compliant, whatever that means