Yes, I suspect its unlikely people would waste atari PCBs these days on repros. That said, they were reproducing using Atari boards when they had loads in stock several years ago. Theres a question mark in my mind over the actual value of any prototype, as many have been reproduced and ultimately a collector probably wants a copy of the game regardless of whether it was the original proto that the others were cloned off. Eg. If I told you that my Road Blasters was owned by John Romero, would that make any difference? Probably not, but it would for a handfull of collectors, with or without proof. At the end of the day the ratity is what actually matters, and since every cart can be reproduced by hobbyists, ultimately we will see more of the rarer games cloned. The trully rare games in my eyes are EOTB, Relief Pitcher, Busty or whatever its called and probably 3 or 4 others that have no more than say 10 copies in existance.

Source: Worth of "released" protos