My rule is just to not give her a reason to hate the hobby. I have a lot of hobbies and side interests, and my wife views them all with the "if it makes you happy, it makes me happy" mindset.

As long as I don't start setting machines up in the living room or spending our car payments on pinball, she is cool with whatever.

In return, I try to be cool about her interests. If there is a bag or something she is coveting, it's no different than me drooling over an AC/DC.

We don't look at it as "tit for tat".

I agree, but I also don't have 8-12 NIB machines. I have a F-14 I poured a thousand hours into to restore, and a NASCAR I saved for a year to buy. Buying a coach bag and wallet is a spend for us as a family, just like buying a pinball machine would be.

I would never just show up with a $500+ pin if she wasn't expecting it to show. I respect her enough to keep her in the loop where our money is concerned, even though I am the single income for us. She is a stay at home mom, but I wouldn't trade with her for all the tea in china.

If she is organized and loves a budget, maybe you could appeal to that.

Work with her to come up a plan that puts a set amount of money aside every month as "fun" money for pinball. Then, it's up to you to save that money up for a machine, or spend it on parts, etc....

She can rest easy knowing you aren't going to screw up all her hard budgeting work, and you can get to spend your "fun" money, no questions asked.