I was playing in adventurer's league the other day, and one other player and I were discussing on trading spells. He was a pact of the tome warlock and had the "Book of Ancient Secrets" invocation. Now as we wanted to trade spells, I was just giving him my find familiar, my DM said we both had to pay 50Gp for him to gain the spell, and we both had to make a check without modifiers for it to succeed.
We stopped it for now, but I tried to argue to him that only he needs to pay the price and that he didn't need to make the check because this was a spellbook, or at least only one the one scribing it and as an arcana check. So with him being new, he said we should go and search for the answer, he did this because he heard other people say this was right. Is it?