Holding an asset does not result in a capital gain. The Tax the Billionaires bill wants to tax holding an asset that has appreciated in value. Not only that, but they use a handpicked time boundary that from the bottom of the market crash to calculate a windfall tax.

Lets say you owned 1 BTC since the inception ($0 cost basis) and held it until today. The value of 1 BTC has fluctuated the entire time, but you've only ever owned 1BTC.

Here are a couple lows/highs during the period: Dec 2018 - $3500 Jun 2019 - $12000 $8500 gain (on paper)

March 2020 - $5500 Aug 2020 - $12000 $6500 gain (on paper)

To use the Bernie Sanders standard of 60% windfall gains, you'd owe $5100 from the 2018 crash and recovery. If these types of windfall taxes become a common thing, you'd owe an additional $3,900 from the 2020 crash and recovery. So you'd have paid $9,000 to hold your 1BTC.

If you sell your 1BTC today, you'd get $10,000. With your $0 cost basis, the entire $10,000 is a capital gain. Lets say your long term capital gains rate is 15%, you'd owe $1,500 in taxes when you sell it.

So for investing in 1 BTC, you'd have $8500 in your bank account, and would have paid $10,500 to hold it.

1) Is BTC more volatile than Amazon stock: Yes 2) Does that amplify the numbers in my example: Yes 3) Is wealth inequality a giant problem in the country: Yes 4) Will I shed tears if Jeff Bezos gets a giant tax bill in the mail: No

However, I think it does demonstrate the problem with taxing the change in value of an asset, vs your capital gain from when you sell it.