I would think that BTC*help is worth at least $$$ as @maxtra has said (although with decline in crypto interest last few months, not as hot a market as a half year ago). Obviously BTC is a great keyword, and there are at least 10 .help extension sales over $2000. If you can find the right buyer, I think low $$$$ might be possible, but the crypto domain is a market crowded with people trying to sell domains. Best of luck with it, @Verhma (and welcome to NPs!).
The other one, I am less clear on to me - other than mining, how would you get free BTC? Still I can see some people maybe wanting it.