For a seasoned engineer the prototyping cost would be lower. I'm sure they experimented with different transformers and operating points but that shouldn't have been too expensive. Still the markup has to cover that cost plus all other aspects of the design.
Whether the amp is worth 10K$ is not for me to say but Todd is only following what others have done. Ray has sold quite a few of horrible "preamps" at insane prices and for most people, MOAR $$$ = MOAR GOOD!!!!
As for Mikhail, the guy used the cheapest crap he could find for everything (often running the parts out of spec) which is why we have hundreds of amps which will not last very long. He also reused parts which could be clearly seen in my ES-1 as the EL34 sockets had cut wires on all 8 pins but they aren't all used plus you have spliced wires all over the place.