When we first started dating, I told my wife about my hobby. I put it as everyone has something 'stupid' they spend way too much on. Bikes, cars, boats, etc for guys; shoes, pocketbooks, jewelry, etc. for women. As long as you're spending disposable income/within your means, buy what makes you happy.
I'll never buy a pair of speakers before paying the electric bill, and she'll never buy a Coach bag before buying groceries.
It's worked for 8+ years. Never a single argument. I know how much her stuff costs, and she knows how much mine costs. We've never looked down at each other's spending habits Never had a need to hide the truth. If I bought something beyond our means, she'd call me out (rightfully), and I'd do the same.