I also keep all my normal income seperate from stuff pin related.
I repair games, sell stuff on ebay occasionally and do side work for CPR to fund any and all pinballs stuff as well as for parts.
This means I can't always buy stuff when it pops up but it also means my wife can't complain about all the money I've spent on this hobby.
On the rare occasion a game goes up for sale locally like a 1000 funhouse a few years ago I've been REALLY temped to make a trip to the bank account...

My profession as a graphic designer and my access to large format printers and materials has benefited me many times in this hobby.
I can make a lot of stuff I might need like 1 off plastics, backglasses, cabinet art and mods.

Blondetall - have your husband keep a nice photo of you at his desk, clearly visable.
This will help.