There may be a little problem with the view that the ATF doesn't care about sales, only transfers. Technically, at the very core of their existence the folks at ATF are tax collectors. I know of a few cases in which the ATF has gone after individuals and dealers because the individual did not pay tax on a weapon he/she purchased from an out-of-state dealer--even though the tax in question was a state sales tax and has nothing to do with the federal government. It was just enough of an excuse for the camel to get its nose into the tent. In order to be on the safe side, some dealers, admittedly few in number, are collecting sales tax on the price of the weapon, even though they are only charging a small transfer fee.
In addition, there is another point on the not too distant horizon. Can't remember the exact date, but I remember hearing about an upcoming regulation that will require everyone to verify the validity of the FFL to whom you send a weapon. It's supposed to work like this. Whether you're an individual or a dealer, you request a signed copy of the FFL from the dealer to whom you want to send a weapon. Then, with FFL in hand, you go on-line or call ATF and verify that the FFL number of the fellow to whom you are sending it is valid, current, up-to-date with regard to address, etc. Somehow you are supposed to keep a record of this. During the ATF audits of the dealers, the auditor is supposed to check randomly somehow on some of those folks who sent weapons to the dealer being audited. Sounds just wonderful, doesn't it?!?! Creates a new class of violation for anyone, private citizens and dealers, sending a weapons withoout proper procedures. Maybe I'm just cynical, but seems the only purpose, beyond making a few more innocent folks into criminals, is to make it more difficult to transfer weapons and thereby reduce the number of transfers. Again, can't remember when all this is supposed to go into effect, maybe already is.