As above, FFL can use USPS, but it means they have to physically send someone to the PO and thats a PITA.
My dealer uses UPS 2 day air, not overnight, I dont think thats a legal requirement. I shipped one a couple weeks ago thru the FFL and its was $133 with transfer fee but I expected that. Told the buyer I would only charge him half and eat the rest, otherwise who is going to pay that much up front and still buy the gun?
It sucks but its the world we live in. My old now retired FFL guy would do USPS for me for about $50 total, but thats over with.