Quite a few new posters lately on the board with really good posts, including this one. Welcome.
I just wanted to add:
6. Cost of lost opportunity. Consider what you could have earned if you were doing something that you do professionally instead of tinkering with arcane software and hardware. Or maybe how much fun you could have had if you've spent this time with your friends and family. How much interest you could have earned on the money you've spent on mining rig, or how much interest you would not have to pay to bankers, or how much profit you could make if you invested it into something else. YMMV, of course.
Very, very, very good point, but not everybody has the same goals/ideals/beliefs, whatever one wishes to call it.
People tend to spend LOTS of time on these hobbies/past-times/activities because they enjoy it. They are here for the buzz.
I tend to spend a crazy number of hours creating game bots and hacks. Not for any financial gain, but just for the buzz of it.
I spend hours every week in the gym and running in the morning, but where one person might exercise to improve themselves physically another may be in it just for the endorphin hit. I'm the latter

Endorphin junky

I thoroughly enjoy studying (currently doing an Open degree with the OU), but have no intent to use my qualifications to improve my job prospects. It's just a great buzz to study

Mind you, I do have a serious problem with authority, which no amount of qualifications will ever help, lol.
Now I'm rambling....
Temporary insanity.... priceless
