These are usually full-custom boards, very low-volume, with many layers and fine pitch traces. The parts themselves may have thousands of pins, routed across a dozen layers or more.

So the non-recurring engineering (NRE) costs are very high, and you don't get to recover them over much volume. Even at 10x the cost, the vendor is still losing money.

I believe it's a technique for filtering out everyone but "serious" customers, because whoever buys one and tries to make it work is inevitably going to ask questions about it.

Um, the FPGA chip on that board retails for $10K according to findchips.com so ... (of course, anyone really ordering these class of chips is going to order them directly from Intel or Xilinx--but that doesn't mean the FPGA will be cheap)

Intel isn't making a lot of money on those boards if they aren't actually taking a loss.

1) A PCI-e board is non-trivial. It requires some engineer to sit down and do some serious signal integrity work.

2) A board with a fine-pitch BGA is non-trivial. These boards generally have via-in-pad and blind vias on the top two layers. The boards are also generally 8-12 layers.

3) The support circuitry on those boards in non-trivial. There's high-speed, fine pitch connectors that are probably in the $100 each range, themselves.

4) Really, you're paying for customer support. You will hit bugs. You will have to communicate with Intel. You probably won't order enough volume to make it worthwhile for Intel.

If you are seriously interested in using 500$ chip in any "interesting" volume, shelling out 5k$ for a dev board is nothing you would care about.

I have an Arria 10 SoC dev board (not the PCI one, the stand alone version). It's a very complex and fully featured board, it's just not just a "breakout board" for the FPGA. It's also clearly aimed at companies looking to integrate an Arria 10 into their designs, not hobbyists looking for a cheap FPGA board and the pricing reflects that.