I walk roughly 5 miles a day. What should I be wearing to keep my shoe costs minimal?

I have been purchasing Timberland boots with inconsistent success. One pair wore down in a few months while my other pair(Expensive Wheat Timbs) have better bottoms but the insides are deteriorating.

As someone who has to walk 5-6 miles per day, what is the optimum shoe purchase strategy to mitigate wear and tear?