FFL fees cost money which then makes a fair deal worthless. And when people ghost, they just save you time instead of dragging you along.
I lived in a state that required FFL transfer for handguns. Most shops charge a minimum of $50 for person/person for various reasons.
If I'm selling a used Ruger for $250, a person has no incentive to purchase it as they can get a new one for $300. Basically, it ruined handgun sales on the used market for anything $600 or less.
Now that I live in a state without FFL transfers, I'm not dropping extra coin for a transfer if I find a used gun I want.
I live in Oregon which requires FFL's for transfers and that costs $50-$60. You hit the nail on the head, the FFL transfer requirement killed used gun sales. Even worse it has push some otherwise law abiding citizens into being felons because of the outrageous transfer fees.