That's the thing. This was a $3000 camera. A 20% friends discount is 600. We've been best friends for two decades, but most days he doesn't give me $600 on cash. Don't get me wrong, we don't keep track who paid for dinner or cinema ticket or whatever. But there IS a threshold at which it really becomes a random cash gift.

Yes dealing with friends is nicer than strangers - but also when you're selling stuff, sometimes it's better to do strangers. Expectations of long term service and support are clearer and have more defined boundaries.