Really good stuff so far and a great topic.
So back when my wife and I got married in 94 she was well aware of my addiction to this hobby. That was when we had a small house, both were working, and no kids, I wouldn't think about dropping a grand on a piece of audio equipment.
Now, I make more than three times as much money but hum and haw about spending $300 on my hobby. The difference is Kids (and that fact that working for a living is highly over-rated and I would like to retire someday). It's not that kid's cost a lot, they do, it's the added pressure on me to ensure they have a good standard of living and ensure they have some type of future.
So this is how I justify this hobby to my wife. I don't own a motorcycle, snowmobile, scuba gear, skydive, hang glider, boat, RV, red convertible sports car (although that is on the list), bar hop or chase skirts. Hell, I don't even fly an airplane anymore. So when I am watching a movie in my dedicated HT room, she knows where I am (home), I am safe, and I am reachable.
For her, these are key. There alot of other hobbies that I could be into that don't offer these things. So she figures, it could be a lot worse.
Ofcoarse the fact that she is a huge NASCAR fan and loves to watch the races on a 130" screen in HD doesn't hurt either.
paul