Tesla and BTC may become obsolete, and there's a chance that no one will use crypto in the future, but this is a remote probability. I won't buy Tesla with crypto, in my opinion, because I know it will be more valuable than Tesla if I hodl for a longer period of time, and I don't want Tesla because it isn't really a thing in my country. I don't see any problem with your decision as long as he's already enjoying life without even buying a Tesla. That's why there's a preference, if you prefer to invest more in crypto, then it's your choice and part of the gamble already as long as you've studied it that you'll make more profit hodling BTC than buying Tesla.