i cant tell you for sure how much just the board is, but in the last month or so I have been collecting a bunch of naomi parts, in the goal of setting up my custom built vewlix with naomi, and building a consolized naomi for my borther.
I purchased a working naomi 2 w/gdrom and cable and dimm from this site for 300 shipped, which i thought was very fair.
I also bought a naomi 1 motherboard from neo/geo for 50.00 it works but has a very loud fan.
I bought a naomi2/ with gdrom and cable, with power cables, and sega i/o board, net dimm and Melty Blood gdrom with security chip and movelist and marquee for 360.00 which i think was fair also, gd rom and dimm work,but i see a heatsink was knocked loose in transit so i cant confirm the mother board works yet or not

but still a good price for gdrom, game and net dimm
i have 2 capcom i/o with cables and i got these thrown in with game purchases, i figure these are going for 140-170 or
So you can take that for what its worth, Im pretty new in naomi scene but i felt okay paying these prices without waiting for weeks for a great deal