> It's the realized gains that get taxed. That's a completely generic feature of the tax system, the government doesn't give a shit (and shouldn't) what people decide has value in any given transaction

If I buy a vintage computer second hand for $1500 and then manage to sell it to someone else for $2000, I don’t owe taxes on that.

But if I buy $1500 worth of bitcoin and then sell those bitcoins for $2000, I owe taxes on that.

So yes, the government does “give a shit” what people decide has value in any given transaction.