1) An item is never cash even if you donate brand new food specifically purchased for a food pantry or brand new toy to toy drive. In those cases the cost and deduction are equal (full price, value method of "comparable sale").
2) When giving to thrift shop, you know that organization is never going to sell your item at full retail price. You have to deduct the benefit the charity will get from it. Your once $20 tee shirt sells for $4. So your cost/basis was $20; your deduction is $4.
