...there is no such thing as "reliable estimates" there is only guesses that are very unreliable too. some of them are of course pretty good guesses but nothing more.
Methodology that those coins who have not moved in a certain number of years are considered lost BTC (say 4), is something that someone can use to do their internal analysis, but as you say it's just a guess that has no solid facts behind it. As we have seen lately, coins from 2010 are often the subject of debate, and it is precisely such transactions that show that we cannot really know what has been lost and what has only been kept in the long run.
~snip~
This has been pretty clear to some for a long time, some others seem to have only recently discovered it, and some still stick to their old stories that Bitcoin will collapse one year in the future. If we refer only to the price, then I would agree that we are still very low considering how little BTC is in circulation at all, and what the total supply is. I remember a few years ago that someone wrote that there are about 36 million millionaires in the world, and only 21 million BTC - I'm sure there are even more (millionaires) today - in other words, I believe that there will come a time when it will not be so easy and simply to buy a BTC, no matter what price someone will be paying.