$BTC is the only asset where you can calculate every holder's cost basis from public data.

It's called realized cap. Coin Metrics dropped this in 2018.

Market cap = every coin priced at today's price
Realized cap = every coin priced at the last time it moved on-chain

Coins sitting since 2010? They're priced at 2010 levels. Probably lost. Barely count.
Active coins? Repriced every time they move.

As a CPA, this blows my mind. To build this for a stock, you'd need every shareholder's brokerage statement. With $BTC, it's just sitting on the ledger.

Yeah, moving coins between your own wallets resets the price too, so it's not perfect. But for tracking what the market actually paid? Nothing comes close.