Unless you miss work or decide not to take up a second job because of your hobbies, you are not losing any revenue by partaking in an activity because in absolute terms, your time is worth nothing in dollars and there's thus no need to factor it in the calculations. Do you also count your "losses" from sleeping, eating and interacting with family ? Sure you could do other things (golfing, reading, etc.), but these other activities do not actually give you a salary either. Sure you have to choose how to best allocate your time, but when you choose to spend your free time doing A instead of B, there's still no monetary value to your time expenditure.
"Sorry honey, I have talked to you for all of 2 hours today, and since my hourly is 30$, it's starting to get expensive. See ya tomorrow at breakfast, or else I'll blow my budget!"
Time is a finite quantity. It's because people have better things to do or just don't have time for the hobby that they quit, not because they reason that at the hourly they earn, homebrewing is just too costly. Hobbies are hobbies, your time doesn't cost you antyhing per se, but it's true that you have less time for other (non money earning) activities.
I have recently planted a garden in my backyard. I have tallied all my costs, but I don't tally my labour. Why ? Because I wouldn't be working if I weren't growing delicious vegetables, I'd be watching TV, reading a book or doing other non value productive activities (ie. I get stuff to eat for cheap when I garden).
