i used to work for a pawn shop. so maybe i can help you out. Most shops in the area are going to charge $25-20 bucks. My shop used to do $25 or less if you were repeat/ multiple gun buyer, or spent some money on stuff while you were in the shop. we used to sell guns at wholesale cost plus shipping plus the transfer fee.
The difficulty you will run into is that most FFLs will only sell to you if you have a valid id from a neighboring state. This was our policy as there are to many local laws to keep up with. And you going to need to have the address match the one you have on your 4473. That means if you live locally you may not have an address that matches your ID. thats a big one. Voter ID, Fishing license or car registration work to verify your address.
The other problem you might run into with AR's is that if you are buying a striped lower, if the FFL is doing their paperwork correctly you will receive it as an other- not designated as a long gun or handgun. And from previous experiences i have found that you can not sell an other to an out of state resident because, in the eyes of the ATF you might build it into a pistol and out of state buyers of handguns are a no-go. We tried and the transaction was canceled.
The previous two statements assume that the FFL is not doing their paperwork incorrect, we were always very particular about keeping everything 100% correct.
just my 2 cents. I worked there for a couple of years, so i have transferred a couple of guns.