I sent the 2 T/A broadcast sheets I found in my car to the cars owner years ago free of charge (I even paid for the postage) and would do the same today.
A few years later the dealer sales paperwork for my car turned up and the seller wanted a pretty penny for it considering it wasn't worth anything to anybody but me. I eventually broke down and bought my sales packet. The guy who had it did put a lot of work sorting through a bunch of decades old paperwork to find documentation for specific cars, so he deserved compensation for that, but it is still a good question as to how much is reasonable for selling paperwork to the only person in the world it has value to?
As far as sending a broadcast sheet one finds in his car to the owner of the car the sheet goes with, other than postage, there is no justification to charge anything IMO. But if someone collected a bunch of sheets over the years from cars they parted or found in cars he owned that had non-matching sheets, and then put time into sorting them out and trying to track down the cars they belonged to, then I think he deserves some compensation for his time.