I've never heard of the 1/3 rule, but if you can get it to work for you, that is great.
After breaking Bushnell, Simmons, BSA (2x), scopes I am now a member of the "buy once, cry once" theory. I'm also harder on scopes because I like to dial in elevation, and shoot at different ranges quite often. So basically I spend a lot of time cranking on the elevation knobs.
The only cheaper scopes I'd trust for any length of time for my uses are the Bushnell 3200 10x, SS 10 or 16x, or Falcon Menace line from what I've heard (never personally tried one). They will run you from just under $200 to about $400 depending on model.
I know a lot of people would rather save the money than shell out for an expensive optic, and I don't blame them. I'd much rather be shooting than eating Ramen noodles so I could save up for a scope. If I could find a cheap scope that actually could withstand the rigors of use that I'd put on it I'd e happy to snag it up.