Fairware Donations

For those who have donated to MSFS freeware authors what would you say is a fair donations for; liveries, sceneries, utilities, etc.?

Obviously, the amount is going to vary based on complexity and usefulness of the item and financial situation.   I have donated in the past with both FSX and MSFS and used my own targets but doing a check-in to see how realistic I've been or should be.

Also, if you're an author feel free to enter the conversation.

Thanks,
Ernie