Depends on the friend. Has he been (and will he continue to be) a friend for life? The guy who I've been riding moto/MTB/drinking/carrousing with for the last 35 years wanted the mounts off my old roof rack 2 weeks ago. We agreed on $25. We went riding yesterday. He handed me the money when he got to my place. I had forgotten about it. If I forgot about $25, I certainly wouldn't get bent out of shape over $80 (50 quid).
I was the best man at his wedding. I think I paid for my tux, but wouldn't place a wager on it (I do remember complaining about the emerald green cummerbund/ties. his response was "do you want to marry her?"). I do know under the circumstances (pending son #1) I wouldn't have had an issue with it.