I like using the term "value" when speaking of equipment or tools, etc. I have always been someone to value function over form every time. That includes clothing, gear, etc. I have spent less money on many items that have lasted a very long time. In general, these items must have a very similar function to the more expensive option. A most recent example is tumbler cups. I was given a Yeti tumbler in 20 oz and it was a great cup. As frugal as I am, I would say that this cup was worth every penny that anyone ever paid for it. That is... until all the knock offs came out and performed similarly, even equally. I bought a $8 20 oz version from a big box store and tested it against my name brand. There is no difference. I don't care about a brand so I would never buy the name brand again.
Outdoor gear... You can often get good quality on the cheap. Yes, even the stuff from china can be decent quality. However, you will usually sacrifice something whether it be weight through use of different materials, versatility due to poor design, etc. A cheap sub- $100 tent has kept me dry many nights but I would never carry it on my back because it is made for car camping, not backpacking.
Tires... let's be serious. No one buys used tires because they are the best option. People buy used because they can't shell out $800 for tires. I have bought used tires in the past but they have been take-offs from 4WD vehicles with tons of life left. I paid $550 for a set of Michelin LTX, with rims for my truck. I drove them for 2 years and sold that set for $500. That is the exception, not the rule. In general, I buy Michelins because the difference in that $100 tire and the $200 Michelin is worth it. My family is in my vehicle often and they are worth a little extra money to me. Peace of mind, if you will. (Look up tire speed rating, safety and performance the next time you consider buying used tires)
But regarding equipment, you really have to look at comfort as a huge factor that you can't place a value on. Does that mean better design in a pair of boots? lighter materials so you are less fatigued? Better waterproofing materials that not only keep you dry but warm and possibly keep you alive.
Look at some of the gear you have in your closet. I bet a lot of it is 10+ years old. Then think of the cost of some of the more expensive, items and do a little division. My $200 pair of Kangaroo Upland hunting boots has cost me about $20 per year to use, enjoy and I love them. Would I have benefited greatly from only buying a $100 pair of boots? maybe but I certainly wouldn't have that $100 bill in my pocket but I know exactly where those lightweight upland boots are.