I LOVE the $10 Argo bag I picked up from Costco a short while back. My only regret is that I didn't pick up more of them for "backup" and of course, the colour selection wasn't the greatest (Costco only carried 2 colours, none of which were the nice black/grey I know they make).
They're pretty well built but still costs more than I'd like from the indie stores I've seen selling them (other styles of the same brand). I like how they have ventilation going through both ends, the front and the top. Surprisingly, the double mesh doesn't make it dark inside at all and air does get through. I tested it looking through the bag with my head mostly inside.
I've been pretty much using that one exclusively now while waiting for my order of 2 leather bags to arrive.