When I talked to my wife about buying my first road bike it was a $2K price tag and she not being the least bit enthused about cycling saw the benefits in a few different ways.
1st - I work hard as the primary income and I was able to justify the purchase because I do get bonuses now and then which is above our primary necessary income. She appreciated that all the over time I work I deserve some sort of pleasure outside of work to compensate for the heavy stress.
2nd - I proved myself responsible as the financial leader of the house by getting us debt free. House paid, cars paid, no kids so I have proved myself to her as being responsible with the money.
3rd - I wanted to ride with club riders because it is much safer to ride in the group around Atlanta and there was no way that I could do this on a mt. bike that I had.
4th - I proved her wrong because she thought I would never use the bike and now she sees that I am addicted.
5th - She has seen my medical status improve because I started cycling due to high blood pressure. That has improved tremedously in the last 2 years. So I am not spending money on medication.
I now have 2 fairly nice road bikes (2004 & 2006) both paid with bonus checks.
Maybe there is an excuse / reason hidden in my ramblings.
Oh....and I forgot the main point.....I gave my wife about $5K for her furniture account so she is free to do what ever she wants with that money.