I have a no diver wife, and she never will, no interest in the sport what so ever, when i first started i just got the gear, she wasn't very happy about it, and she is a very smart woman, so she knows how expensive the gear could be, when she notice how happy i was to go back to do something i loved so much and i had left behind for years, she was ok with it, i think i have more stuff that what i really need, and she knows it, one thing that has work for me when she question me about a new toy i mention i got it for safety reasons, that works well, other thing that use to work was bringing home a couple lobsters or crabs home, but now since she is pregnant no more fish for her, so i have to figure out something else, one other think that had helped me is when i first told her yes is lots of money but this gear should last for at least 5 years or more, renting is expensive, i wouldn't say i dive a lot but i do around 60 dives a year, so it justify the expense, but i think what really helped me out is when she realized this activitie made me very, very happy, sometimes i get home before she does from work and when i'm in the computer she smiles, look at me and ask me the same question every time, Scuba Board? my answer is always the same too don't you know by now? she shakes her head and walks away mumbling something i can't never understand, but inside she is very happy for me.
Other thing that helps is getting her that nice bag with the matching shoes.