Agreed, but since no one knows how many coins are "lost", how can the market be functioning on the premise that x amount are gone? If 100,000 bitcoins get moved for the first time in 5 years, were they just being held long term, or were they "lost" coins which have suddenly been rediscovered? Did the market already price those in? We don't even know that Satoshi's coins are truly "lost". And if we know that someone is going to break ECDSA in the future, can't the market price that in in advance as well?

There are too many unknowns, but everyone should be operating on the premise that the current circulating supply of bitcoin is 17.9 million.