It will be difficult to correctly estimate the total number of lost coins. Some old dormant wallets which are suspected to contain lost coins can suddenly become operational in the future. In economics, the availability of an asset usually affects the price. Lost Bitcoins reduce the number of Bitcoins in the market which will slightly increase their worth. The higher the number of lost Bitcoin the more valuable the worth of Bitcoin.
I don’t even consider bitcoin been lost if they are actually still on a spendable address, many people consider bitcoin sent to a wrong adress as a lost coin, although it is not common but I believe if bitcoin is sent to an address that is with a correct checksum that particular bitcoin isn’t lost because there is tendency of it been spent. The only validly lost bitcoin is that sent to a burn address, like using the the usual OP-return method which means the output can never be spent, this is the only way the coin is lost in my opinion. Right most of all this assumed lost bitcoins could be long term holders who left it dormant