Most of the parts are SUPER precise. The jewels would be hard to fake. Assembling a 3D spinning tourbillon would require VERY skilled labor. Creating a one-piece Sapphire case would be very expensive.
All in all, the rep - using only cheap jewels and Stainless Steel parts - would still require an enormous investment for some of the equipment, an enormous investment to get skilled watchmakers to assemble a 3 axis tourbillon among other complications, and ensuring that people would pay a higher price to justify all of the up front cost is a huge risk.
A rep of the Astronomia wouldn't have the same precision on the star maps or the globe of the earth. Creating different versions, like the Noob sub for instance, would be expensive and the demand might not be there given the expense.
I'm thinking the rep would cost somewhere in the range of $5-8k. But even that is probably too low of a price.