I'm interested in finding flats with better looking dimples than Tapco's present production. I liked the old Hesse/Vulcan flats better. With all the new Bulgarian '74 kits available I think flats made specifically for the AK-74 might be a viable market, with a smaller mag well and no holes for the trunnions so you could make it work with rear trunnions from both 47 or 74 as well as the folding stock.
BTW,Your selector marks look great!!!
I also think you are right about a $100-120 receiver being a very hard sell. Just my 2 cents.