Agree with everything Alexh said, but I think there's a market for an SDRAM (or other fast) RAM provide your own 060 mainly for improved memory speed and compatibility, and as a combo expansion (clockport, HDD interface). That market is likely as lucrative as for the 1230, the price can be about 330 EUR without CPU and the whole batch would be sold. No, I don't know this, I'm projecting this from how many people like me there are left
There's a few problems. 060 requires nonstandard PSU, and > 50 MHz may require expensive RAM or make 1:1 memory cycles difficult to achieve. But even 2:1 memory cycle, I would buy an equally performing 060-80 MHz with 512MB RAM for 300-400 EUR, just to have a newly made modern component that I can rely on and can follow into the future.
The other way (to get out of relying on CPU supplies) is 'any MMU M680x0 in "FPGA"' at extreme speeds, but that will raise the price.