Same way that if I go to a movie, I don't typically think about it as costing me the price of a ticket and 2 hours of wages (although technically I could, I guess). I calculate time cost for things that I don't want to do.
If anything I would use the time spent in the value calculation (I payed $13 for 2 hours of entertainment).
I also agree 100% with the time cost on something you're wanting to learn is a sunk cost. After all, it's an investment in yourself. Even if it fails, you now have that experience of what not to do if presented the chance again.
If you can travel by public transport, part of the time of your commute is akin to leisure time. But I have big issues with failing to focus, especially if I gotta switch transport multiple times or run to make it or its crowded or...
My limit of commute is basically an hour, and if I don't get the costs reimbursed I simply do not take the job. It is bad enough that I lose that time as it is (as I argued above, it is hardly akin to leisure time).
As for the topic at hand, I've spend a good amount of time and money on e.g. old UNIX hardware (such as SGI Indy/Indigo 2/Octane, Sun Ultra 10, and some DEC Alpha machines) back in the start of this millennium. It was costly and bad for my electricity bills, and it took me a lot of time to play around with old platforms. I had a lot of fun though. And I'm not sure you can benchmark "fun". Nowadays, with solar energy on the rise, it might actually matter less to have these machines running. Except for in the summer. The additional heat would kill me.
Learning to think about time spent on getting ready for work and commuting to and from work as a direct extension of my working hours changed the way I looked at jobs and approach salary negotiation. It's so easy for someone to ignore that cost if they haven't thought about it, and so hard once they have thought about it :)
Then ran extension cords from all over his house into his garage to power the things, networked everything together, and played with it for 6 months, mostly over the winter.
He said he was able to break even (that is, mined enough coins - mainly other alt-coins, not bitcoin) to offset his costs in both electricity and what he spent on the hardware. Kept his garage closed and the door to his house open, and it heated things fairly well from what I recall.
In the end, though, he shut it down, because it was starting to go upside-down for him; I don't know what he did with the hardware (he ended up giving me one of the GPUs - so maybe he parted it out for friends to upgrade their systems?)...