How much money has been invested *into* Bitcoin, in total?

Need help thinking this through. I can google answers for market cap, but that’s not what I want. I want to know how many $$ have actually been put into the asset, in order to know how much liquidity is there if people try to sell.

I totalled number of bitcoins mined each year, and average price each year. I assumed each coin was sold in the year it was mined, at the average price.

Result, lifetime inflows into Bitcoin of $21 billion.

How reasonable are my assumptions? Are there better approximating methods? Clearly not every miner sold, making my estimate too high. Or some may have waited to sell into the boom, making my estimate too low.

I’m counting the inflow as the first sale of a coin, as that is when it moved onto the market and became a traded commodity. That represents capital flowing into the bitcoin ecosystem.

I am asking this in light of Tether and Defi. Tether printed about $30 billion tokens in the past year, falsely claiming they are backed by dollars. If my numbers are right, this fraudulent $30 billion inflow dwarfs the lifetime inflow of hard currency into bitcoin.

Similarly, in the past six months Defi has exploded from almost nothing to having $40 billion in loans denominated in crypto, with crypto as collateral. This total also dwarfs hard currency investments.

Centralized crypto finance has seen similar growth. From nothing two years ago, now likely over $40 billion in loans. Both Cefi and Defi pay 8-12% interest on deposits, which is a higher interest rate than junk bonds pay.

So:

1. Are my estimates back of the envelope plausible?

2. Am I right in thinking that is it extremely worrisome that hard currency investments into bitcoin are 5x smaller than fraud and crypto debt inflows? And that the bulk of the latter happened in the past year?

I worry there is a Lehman like situation brewing where the assets everyone treats as valuable for collateral are worth much much less and could collapse at once.