Suppose you have the option that with every purchase you make, you can divert a percentage (including 0 and 100) of the money to a GiveWell endorsed charity that you're not personally affiliated with. Meaning, you still pay the same price, but the seller gets less/none, and the rest goes to charity. Seller has no right to complain. To what extent would you use this? Would it be different for different products, or sellers? Do you have any specific examples of where you would or wouldn't use it?

Also, assume you can start a company, and that the same thing applies to all purchases the company makes, would you do it? Any specific business?