Of the 21 Million BTC that will ever exist, it is estimated that 3-4 million are gone forever....Mainly due to the early days, old computers thrown away and forgot they had a wallet. There was a story a couple years ago of a guy searching a landfill for his old computer he threw away...Back then, it was $127Million... https://www.cnbc.com/2017/12/20/man...bitcoins-and-city-wont-let-him-look.html

My old neighbor (who is now deceased RIP) that I used to have work on my computer had a wallet from the early days and sitting on an old hard drive... He never wrote down his private keys and literally had $1.5 - 2.0 Million in BTC he could not access. Obviously that doesn't happen today as people use hard wallets & cold storage but in the early days, it was just a tool for computer guys, gamers, miners that didn't have the foresight to what it is today and the Trillion dollar asset that institutions are trying to acquire.

But the really crazy one is the guy - Laszlo Hanyecz - that bought 2 Papa Johns pizzas for 10,000 Bitcoin back in 2010, then worth ~$30 - hailed as the very first BTC transaction..... Those BTC for those pizzas today would be worth ~370 MILLION!!!!!!

So when you take the scarcity of BTC of 21 Million, less the 3-4 lost forever and the ~1,000,000 in Satoshi Nakamoto's wallet... Around 17 million will ever be available for buying, selling, trading, exchanging etc...