(Legitimate) tax deductible donations aren't no-cost. You can only use it to reduce your tax at the marginal rate you pay. If, for example, you were in the 30%

(Legitimate) tax deductible donations aren't no-cost. You can only use it to reduce your tax at the marginal rate you pay. If, for example, you were in the 30% tax bracket and gave a $100 deductible donation, you'd only reduce your tax liability by $30 (ignoring edge cases) - ie you're still $70 out of pocket.