ericgus wrote:right now AFAIK no one is doing that.
Not correct. Some people are selling the boards: viewtopic.php?f=117&t=32121
And it seems more boards will be available soon.
MiSTer is more safe in term to follow the project and provide support. It's fully open. Custom boards have no complex or hard to find parts. So, it can be produced by anyone. Also, you always can save some money if you are willing to make it by yourself. And it's very cheap if you will do.
In case of fully custom boards you usually have to pay 2x 3x price due to very complex assembly and high margin of manufacturer. And of course you depend very much on producing quantity. For example, FPGArcade is always lack of supply and while waiting for free availability it become outdated already. Even Xilinx development environment stopped to support the FPGA used in FPGArcade. And price is 3x-4x times higher than DE10-nano which has bigger FPGA.
With current situation on the market where FPGA has only small fraction of market, the price for fully custom boards like MiST or FPGArcade will be very high without offering even small part of emulation comparing to dirt-cheap RaspberryPi.