You wont see NATAMI at that price...
Minimig is 160 euros, yes... basic configuration... add 4 MB(68 euros) and ARM controller and it will be around 300 euros.
C-one is 333 euros.
These are all significantly less powerful computers with smaller FPGAs then Natami.
If anything, you should compare it to Atari Firebee(599 euros no VAT), which has a dirt cheap Coldfire and a smaller FPGA, but it is at least comparable in power and add ons. First models with 68060 will be even more expensive.
He's right. The NatAmi will have a much larger FPGA than the MiniMig or even the Retro Replay board. It will probably cost around 750-850 Euros for the prototypes and only after the bugs are worked out will we have a Altera HardCopy version of the FPGA made (assuming that's still the most cost-effective technology for making fixed-functionality chips).