The curve for utility for dollars spent starts out quite steep but levels off quickly. A $4 backpack, pillow case and scrap line, is cheap but a big advance over not having anything. The difference between a $100 and $200 pack is small. The functional difference between a $1000 and a $1200 pack often imaginary.
There is also the happy trend that the general level of quality is pretty good and getting better. The steel in discount store knives has progressively gotten better. High quality steel, particularly stainless steels, has gotten cheaper.
ireckon makes a good point that replacing O-rings is a good way to save money. The easiest place to get the silicone grease he mentions is to go to the plumbing department of any hardware store and buy a tiny pot of "plumber's grease". This usually comes in a tiny plastic jar, about an ounce I guess, that is about as big around as a silver dollar. Sells for less than a dollar. One ounce is pretty much a lifetime supply because you just need a dab. I always lose the tiny container before I use it up.