As long as you're paying your bills and necessaries ; if you have some money aside for buying a knife , there's no need for justification from anyone else what you buy. If you earned that money ,it's up to you how you see fit to spend it. If you need to get approval from someone what to spend your money on , then there's something wrong there. It's your money.
+1 here.
My wife knows how frugal (not cheap) I am. To purchase items I use coupons, buy in bulk, purchase items on closeout/clearance, attend yard sales, search a lot of internet yard sales (ebay, craigslist, for sale forums), wait for retail sales to occur (food, clothing, electronics, etc) , save my spare change, etc... I engage in these practices on my own without her encouragement. Priority #1 is my family and their well being. So mortgage, food, clothing, utilities, etc. come first. As a result none of my "tool/gear" purchases are questioned.
So long as you have proper money management habits there should be no debate as to what to spend your money on.
If you are unemployed, rely on parents for finances, or have horrible spending habits then that is a different story.