I get it.
You can do the right thing, know it is the right thing and still feel bitter about the cost.
I knocked a wing mirror off a parked car in a residential street (crap driving I admit, peeing it down with rain, late for an appt, desperately scanning for somewhere to park etc but it was wholly my fault). The car was old and battered and the wing mirror was fixed so didn't 'snap back' like a modern one.
The owner was nowhere to be seen, no answer at nearest houses so I left a note on the windscreen with my contact detail and an offer to pay.
It took 2weeks for her to contact me and, rather than the 40 quid for a new wing mirror from Halfords I thought it would be, it was hundreds of pounds because the car was so ancient that the part couldn't be sourced.
I really doubt the car was even worth that much.
I said if it was that much I'd need to go through insurance but she hassled me and made me feel guilty about her not having a car for longer.
I felt a bit suspicious about the cost and her attitude and asked to see the garage bill and pay them direct but it was indeed true (unless she is a very sophisticated fraudster with a tame garage)
I may indeed have commented privately to DH that honesty is not always the best policy but I knew that bottom line it was my fault so of course I paid up.