Well, “willing to pay for warm fuzzies” is a bad way to put it IMO. There’s limited amount of money available in the first place, if you care about birds rather than warm fuzzies that doesn’t make you a billionaire.
The figures people would pay to save 2000, 20,000, or 200,000 birds were $80, $78 and $88 respectively, which oughtn’t be so much that the utility of money for most WEIRD people would be significantly non-linear. (A much stronger effect IMO could be people taking—possibly subconsiously—the “2000” or the “20,000” as evidence about the total population of that bird species.)
The figures people would pay to save 2000, 20,000, or 200,000 birds were $80, $78 and $88 respectively, which oughtn’t be so much that the utility of money for most WEIRD people would be significantly non-linear. (A much stronger effect IMO could be people taking—possibly subconsiously—the “2000” or the “20,000” as evidence about the total population of that bird species.)