If you donate appreciated assets, you don’t pay taxes on the appreciation, so in the best case scenario (e.g. you bought bitcoin at a penny) you donate $100, but it is the equivalent of $80 after tax.
Additionally, you get to write that $100 donation off your income. If you’re in the highest tax bracket, that means you’re saving $39 off your tax bill.
You’ve effectively given $100 in exchange for the cost of $41.
In your example, the donation cost the donor $100, which is much more than the tax reduction of $39 + $20.
But on another point, didn't you just double count the tax? You donated $100 of bitcoin, and you write it off your taxes (so not having to pay that $39), but you just counted another $20 somewhere.
So from a personal balance sheet the options are: Donate $100, reduce taxes by $20. (Net expense $80, cash in pocket $0) Cash in $100, pay taxes of $20. (Cash in pocket $80)
The donor still gets more cash by not donating. The difference is that they can get more value by donating. In the sense if they donate to a cause they can spend $100 plus the $20 they would pay in taxes for total impact of $120. If they spent it on a taxable cause then they would spend $100 get $80 in impact since they would need to use $20 on taxes.