It's really saddening that something like this has happened. Even before this, no matter how tempting the item might have been, I would have walked away if I had seen F&F only as a payment option. Friends and Family is just that; it's "Here's that gas money I owe you!" It is categorically NOT for paying for high-value items. They are Goods and Services, as that is what you are paying for. I don't know what fees are imposed when this method is used, but the seller should either wear them or incorporate them into the price in order to recoup them.
In the past, whenever I have bought items on FB, and no method except Paypal has been specified, I've always paid G&S, and nobody has complained. Going forward, I think it should be a general rule within One Sixth Indiana Jones that ANY item for sale must be paid for via G&S without exception.