So the M-class mechanism is completely wrong. The Bachmann 2-8-0 has 63" drivers while the M-class all had 56" drivers. Id be interested in buying the boiler but a completed inaccurate model is WAAAAAAAAAAAYYYYYYYY overpriced at $750.
They won't sell many if any of these.
Drasko
Well, their description does say "we heavily modify to make it accurate for the M class"
They don't show any photos, so it's impossible to know what "heavily" means. But I suppose it's possible they changed out the drivers.
A 7" driver size reduction would be .043" in N Scale, so they would also have to scootch the drivers closer together, which means major changes to the frame, or their own frame, and of course, modified or new siderods.
Even if they did all that, I agree with you that $750 doesn't sound at all like a practical selling point for the model.