No. As a charity donation, you can only claim the amount that is more than the fair market value of the item you purchased. If the item is worth $80, then only the $10 "overpayment" is a charity donation. If the amount is worth $100, then nothing is a deductible donation because you paid less than fair market value.
Furthermore, the organization is required to give you a receipt or letter of acknowledgement when you pay them $75 or more, that indicates the value of the benefit you received, and any tax deductible value. If you don't have that, you can't claim a deduction.
