So I'm not saying I understand what will happen with Bitcoin long term. Or else I'd be on my own big boat right now.

I also wouldn't take your bet as I think bitcoin likely will go above 30k in the next 4 years. What is also likely is that the price will remain volatile - unless there's a major game changer I think this volatility will keep putting a lot of people off (with an impact on price).

I have no idea what the price will be in 4 years time. My guess says under 50k. But I wouldn't be surprised if it hit 200k.

You're writing OP, an almost perfect put. Although I have no interest in BTC, and would never take someone up on a bet like this, there's almost no upside on this bet for you.