A few threads ago the cost of the device came up, and I believe $400USD was mentioned.
I know that there are other FPGA / FLASH based devices that are very popular for other consoles (Everdrives, SD2SNES, etc) but none of them are close to this price range. Most are 1/2 price or less (and yes, they too are designed by a single developer who spend hundreds if not thousands of R&D time making them)
I think as the time gets closer, it would be nice to go into detail on what makes this thing tick (in terms of hardware, etc) because $400USD is a lot of $$$.
Back in the day a Sega Genesis or an SNES were $100, but the Neo Geo was like $600. It's the same with its carts, they are way more complex than the Sega Genesis or SNES ones, which usually have a single data chip inside. The Neo Geo has 5 different buses, all working in parallel to bring the nice graphics and sounds we are used to. So the neo's multicart has to be way more complex, therefore way more expensive than the ones for smaller, less complex consoles.