Personally, I wouldn’t put anything in a gig bag that I couldn’t afford to replace. That said, there are gig bags and gig bags. I did come across Tim O’Brien on a flight out of Wellington NZ, with his Nuggett mandolin in one of those rigid foam filled jobbies - forget what they’re called but you can’t get them in th UK.

As for a pile of Brazillian rosewood firewood, a mate of mine did just that with his D28, in a gig bag, on his back, ski-ing home from his local session.