I generally carry an Opinel, so their is no 'should I loan this knife?' type dramm
but when I carry my opinel #8 an my gec #15 at the same time and I and the another person both have cutting tasks I generally give the other person the gec (for those of you who don't know my gec can sell for about $90 US)
if a knife is damaged/lost I don't generally replace it(unless its an opinel, am have grown very fond of them), and I don't usually sell my knives so in my mind the value of the knife is based on how much I like it not its retail price I like my opinel, and although I also like my gec it simply isn't worth as much to me.
in summary unless you plan to sell it the decision on weather or not to carry a loaner should be based on how much you like your knife not its original cost a
small opinel(perhaps a #5) would make an affordable loaner if you decide the knife is worth it then you then you can protect your knife, avoid being a jerk, and avoid giving more money to the makers of low quality knives for almost no money and very little pocket space