This was a really interesting reply, thanks. I'd leave a longer response, but honestly I really need to be asleep right now.
If $120,000 is a bit much for you (it's still far less than would be required for a Bitcoin mining farm)
I will say though, even today the barrier for entry is lower than that for bitcoin mining. You can definitely get started for $1000. I wouldn't really recommend Bitcoin mining as a hobby at this point, but that's basically the low end for a single machine.
Personally, that's about as much as I ever spent on mining equipment, and it was fun, I learned a lot, and it was even lucrative in the end.