" Is there a difference in the amount donated—based on the "suggested donation" you list? Desmet (1999 ["Asking for Less to Obtain More." Journal of Marketing Research, 29(4), 430–440.]) found it depends on which suggestions you manipulate. Suppose you have the following "suggested donations":
•$15
•$30
•$50
•$75
•$100

Desmet's research suggests that changing the $30, $50, or $75 will have little effect, but raising the top or the bottom number will have significant results.

In his research, raising the top number led to overall larger donations. Strangely, raising the bottom number led to significantly lower response rates. Why would raising the $15 cause fewer people to donate? The dropoff came from previous donors who had contributed a small amount. Desmet cites an "aversion to the extremes," whereby donors do not want to contribute the smallest or the largest amount on the list.

So adding a $125 choice would increase the number of people who donate $100. But if the lowest number shown becomes $30, then people who donated $30 before would now be donating the lowest amount listed—which they don't want to do. Instead, some of them may choose not to donate. "

― Marlene Jensen , Setting Profitable Prices: A Step-By-Step Guide to Pricing Strategy Without Hiring a Consultant