Here's my theory. It doesn't matter if it's guns, cars, house work or anything.
1) Allowed or estimated budget.
2) Expectations from the money spent.
This typically works well for me unless I take an unexpected left hand turn changing directions in the middle of a project. I've learned over the years to buy the best that I can afford otherwise I end-up spending the money again upgrading parts (I hate spending money twice re-buying parts, but it happens). It's an individual thing, everyone has a different situation, budget, and expectation.
Sort of like the "need / want" struggle. Good luck to the OP