Except that in your scenario why would anyone mine at $20 and hold when they could just buy at $10 and hold, doubling their return? With super-low transaction a

Except that in your scenario why would anyone mine at $20 and hold when they could just buy at $10 and hold, doubling their return? With super-low transaction and storage costs, there's nothing special about the BTC I mined relative to the BTC I bought.