How are authentication opinions priced?
In short: A flat fee per card, quoted in writing before I start. The same basis applies to pre-purchase second opinions, in person or remote.
The fee is the same whatever I conclude. If it were higher for a "genuine" finding, or tied to what the card is worth, I would have a reason to lean one way.
The quote states the number of cards, the fee per card and whether the work is in person or from photographs.