You wouldn't be selling those on the open market, institutions have been able to acquire billions of dollars worth of crypto OTC without moving markets.
Another option is, now that it's becoming clear to people that Bitcoin is here to stay, you can just borrow against it to spend (avoid taxes, hold on to the upside). Case in point, this person/group borrowed 300M$ with about 1B$ net worth[1].
I still don't completely get the borrowing against your bitcoin. You'll end up having to pay that back with interest, so it's going to end up costing you more assuming the price stays the same.
Are people just banking on the assumption that it's going to go up higher than how much they have to pay back over time? What if that stops being true 5 years from now somehow, like another coin becomes dominant? Not saying it's likely, I do think Bitcoin will probably still be doing well in 5 years, but I'm not certain of it.
The interest rate varies based on collateral: https://oasis.app/borrow/markets. Eth is between 3-9% depending on liquidation ratios, and wBTC is at around 4.5% and both of these numbers are drops in the bucket when you consider that the collateral has appreciated a lot more than that.
And one more thing, it's not technically an interest rate, it's a stability fee (which btw, gets burned, used to go back to stakers, but they removed that).
Okay, so I suppose the stability fee is paid in MKR, and Dai's stability ultimately is regulated by people who buy MKR, and because MKR is burned by the CDP, people who buy MKR receive the "interest" indirectly due to deflation of MKR? Though MKR is independently traded and seems to move far more from trading than deflation.
It's just a smart contact vault, you can put collateral, take it out whenever you want, you just need to make sure that at any given point in time you have at least 150% of your debts value in collateral in the vault. This person is at over 400%, so very conservative borrowing, can withdraw some collateral.
There are also centralized versions with blockfi if you prefer traditional loans.
It handled the black swan event of complete market crash at the beginning of the pandemic pretty easily. And the other thing is Bitcoin's market cap is well over 1T$ now, as expected the volatility goes down as the market cap goes up. I suspect those ratios are going to come down significantly within couple of years.
In practice, cashing out billions of dollars worth of stocks is easier than cashing out billions of dollars worth of crypto.