as for the whole idea of "borrowing" lenses, i never liked that idea.
the cheap lenses, i never saw a need to borrow. can just buy. dun like, just sell. of course, if u must borrow, the risks are much lower. pple have a higher threshold for cheap lenses. scratch the lens hood / lens barrel on a tamron superzoom? no problem... small case.
the expensive ones, i am neither willing to lend freely nor would i dare to borrow if bo tai ji, then its great. but there's just no end if something bad happens.
imagine knocking a canon L lens, a sony zeiss lens or a high end nikon FX lens against a railing... its just a tiny bump, maybe u scratch the lens hood, or there's a slight scratch on the lens barrel. the owner definitely won't like it. they'll whine a bit, u won't like to hear it, and before u know it...