I bought merch from a 501(c). Turns out they considered the transaction a donation. I received the stuff along with a receipt showing the cost of the merch deducted from the total price, so the remainder was a tax deductible donation.
For example:
Donation (what I paid): $50
Estimate fair market value of gift (merch I bought): $28
Amount of donation in excess of the fair market value of gift: $22
I can claim a donation of $22 to this charity from my $50 purchase of merch.
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