I don't think revenue from transfer sales is exempt from the $1,000/mo limit. I think it all counts (guns, transfers, accessories, ammunition, etc.)
So at $1,000/mo, you are looking at 20 to 50 transfers depending on how much one charges. Expect transfer prices to go up as available options decrease. Besides, as a business owner looking at a cap of $1,000/mo, do I want to do 20 transfers for my $1,000, or 50? Can't make it up with volume in this case....
And I can say from experience, a transfer is a minimum of 30 minutes, more like 45, these days. It takes longer to get the information entered into the WSP system, printing out applicable forms to sign, plus the fact they have to come back in 10 business days to pick it up (counting that in the 30-45 minute portion). Old days, I could get a non-chatty-kathy in and out in 10 minutes for everything but pistols, plus whatever time I spent sending out FFL copies, waiting for packages, opening boxes, processing, recycling, etc.
From the first contact (Hey, I bought a gun, can you send your FFL to XYZ Guns?) to them actually taking it home, I figure it's an hour of work.