That's a really good question jppe. As long as your cycling costs don't interfere with your families needs, maybe you should look at all the positives you gain, like improved health.
I get my bicycle purchasing 'fix' every weekend when I go yard sale-ing. My kids and I now have 10 bikes. But you know we 'need' almost all of them.
Fortunately, I buy most of them for less than $25. My wife doesn't say a word as long as I keep on cycling and getting a workout.
She's the one who talked me into buying that new Specialized FSRxc Comp. It cost just a little more than $25. Her justification: if it keeps me cycling and getting a work out, it's worth it.
I draw the line and stop buying when I think it interferes with my families needs. Otherwise, I keep my interest going.