Correct me if I'm wrong, but I believe charity contributions can only reduce your taxable income. For simplicity, let's say you have an income of $1M and a tax rate of 35%. Normally you'd pay $350k in taxes. If you donate $100k to charity, then you pay 35% * $900k = $315k in taxes, for a total payout of $415k.
The real picture is a bit more complicated than that due to variable tax rates, but I don't think there's a case where donating to charity doesn't increase your total payout, since you give up 100% of what you donate instead of whatever tax rate you'd have paid.
The real picture is a bit more complicated than that due to variable tax rates, but I don't think there's a case where donating to charity doesn't increase your total payout, since you give up 100% of what you donate instead of whatever tax rate you'd have paid.