I think your best chance for a great deal is finding a complete cabfor sale and the seller has no idea that the game runs on naomi hardware. Usually by the time a game is parted out someone has figured out what it is worth. I got a complete naomi system in a cab w/CD player for $100. Took out the Naomi and sold it for $350 and then put in a Marvel vs. Streetfighter in it and sold the cab for $300.
GD-ROM drives run anywhere from 100-180 on ebay. Normal Dimm boards run about 60-90
and net dimms run from 160-200
the scsi cables run about 30.00 each (you can buy a scsi from monoprice for 6.00 but they are out of stock on them right now)
If you have a net dimm already you can convert to compact flash.
I have the CF gdrom drives for 125.00 (150 with a game card of your choice).