I think in at least some cases, they are trying to convince themselves that the money they spent was on the best possible gear.
I know that every bit of gear you buy is a balance between weight, utility, cost, personal preference and a host of other variables.
Backpacking stoves are a perfect example. I love my Whisperlite, while my (equally experienced) hiking partner loves her Jetboil. Is one clearly better than the other in all respects? No- each has their advantages and disadvantages. It really comes down to what we prefer and what we perceive as best for us.
The same goes for knives, tents, etc., etc.
The ones who have to brag about their stuff being the best of the best are mostly trying to convince themselves, IMHO.