I'm a believer as well Jeremy, have been using cricket bat bags and hockey stick bags for tripod/monopod for some years now. Some also have a handy pocket on the outside, which fits a light shower/rain cover....for me or the camera
Another one to check out is rifle/gun bags, I find light stands fit in these roll up bags.
Anything purpose labelled 'photography' equipment seems to be more expensive!
I have also purloined my daughter's hair straightener bag and portable iPhone speaker set bag.
1 of which fits the gorilla tripod, I have the largest 1 of these for travel & the other has the pocket wizards.
Anything with some padding & the right sz & shape, is worth a look.
And working back the other way camera bags or backpacks that sit flat and can have the top opening sort of peel back (if that makes sense) are fantastic for sports team first aid kits!
I put a Lowepro bag which my gear has outgrown into service this way. It offers very quick access & all the items are kept seperate & easily located. Purpose first aid backpacks open from the top & everything is on top of something else & useless in a hurry!