So why don't 01 FFL's just convert to a type 07 you ask? Lots of reasons. Zoning is a big one, as a location that's good to go for retail sales (01 license) may not be ok for industrial activity (required for an 07 or 10 license) without a variance (money and attorneys required). Further, 07 and 10 licensees must pay ITAR annually to the US Dep't of State ($2250/year). Many gun dealers are scraping by as it is, and the additional fees and regulations could force them to close up shop.
2,100 dollars is pretty expensive, the Federal Government has shed FFL licensees for years now, especially when Clinton raised the fees and chased many many FFL holders out of the business.
There were some machinist types who were making 80% receivers, I think that is one of the points behind the new regulation(?)