> Collateral IS the risk premium. It defeats the purpose of asking for collateral if the collateral is itself so risky it has to be offset with higher interest or can only reliably back a tiny percentage of its nominal value.

First, let me remind you that this is a hypothetical that we are discussing. That being said, the volatility is not this needle that moves from $0 and Current VAL.

If I have 3.5 billion dollars worth of BTC or 3.5 billion dollars worth of TSLA shares and I want to have 500 million dollars of liquid FIAT, I'm not going to sell 500 million in BTC on the open market nor am I going to sell 500 million in TSLA shares on the open market. I'm going to find a market maker and use the assets as collateral for a loan from a market maker. I'm going to pay them interest and likely negotiate a deal which specifies how obligations are to be paid by X date if there is not Y payments made or if the BTC/TSLA shares drop Z%.

This isn't a rare or unusual thing and it depends entirely on what the assets are, the size of transaction, as well as the private individuals involved in the deal, along with their perceived capabilities of repayment.