As far as hobbies go, this is actually pretty mild in the context of how invasive it is to family life. Saws don't take up very much room. (They take up less space than my ex wifes shoe collection) It doesn't require a lot of money; and has to be the least expensive hobbie for guys who want to play with things that have engines on them.
Another reason you can play this game on the cheap is that many saws can be found sitting around unwanted and just taking up space. They can be had for just a few bucks or less. I have an advantage being a shop owner, but I had put the word out that I needed a Jonsered 920 top end for a buddy of mine. In walks a guy with THREE 920's followed a day later by a guy with a 910. All for free. I just had to spend $10 for a mount on the 910. So I add a 910 and a 920 to my collection, and my friend gets what he needs plus some extra parts.
Of course, the guys who are into the new saws with expensive mods have to lay out a few bucks, but even this is cheap compared to most other hobbies. I probably spend $2000 a year playing ice hockey between the league fees, equipment, driving, etc. Guns, snowmobiles, racing, ATV's, hot rods. Try to find something that costs LESS than saws.
And once you start to use the word "collection", you don't have to justify adding to it.
Or we could try a trick the girls always get away with. How many times do they buy something they want, and justify it by saying "It's for the house"?