To be clear, you're being taxed on the asset's value, not on the unrealized gain. This conversation seems more like:

- you make $100k a year

- you pay $20k in taxes

- one year, you buy a house for $400k

- in the next year, its value doubles to $800k

- I say "your income (including unrealized gains) last year was $500k. You only paid $20k in taxes. That's only a 4% rate! How unfair!"

Among other things, I find the whole thing silly because of course it'll only be used to criticize the low tax rates of people who have unrealized gains. If Amazon crashes and Jeff Bezos's net worth goes down by $20B and he pays $100M in taxes, no one will write an article about how unfair it is to tax the poor guy $100M on his incredibly low income of negative $20B. Poor guy, he'd probably be the lowest-income person in the whole country!