Asking the "final" price of Bitcoin is useless unless you were talking about within a certain time frame. You may as well ask what the final value of USD, EUR, Dogecoin will be.
what the hell is it with people here and reading comprehension?
here is the question again - How MUCH will the FINAL BTC be WORTH?
that therefore means what will the price be of the final bitcoin to be mined?
now answer it correctly.
Ah, to me the "final bitcoin" was the last bitcoin used (transacted). People saying that they know now when the final bitcoin will be mined, are making several hypotheses already:
1) that the few lines of code that determine the emission curve of bitcoin will not be modified. If the current emission scheme remains intact, indeed, the last Satoshi should be mined around 2140 or so, but in fact, these lines can be changed just as much as the block size can be changed: these are two scarcity parameters (one in the transactions market, the other in the satoshis market) that are not guaranteed to remain immutable.
2) that bitcoin will not fork over the ages in a miriad of competing chains, or that even the notion of "chain" gets abandoned.
3) that bitcoins will keep all of them the same price, even though bitcoins are not fungible (each one has a specific history, for instance, it may be that satoshi's original coins, if they start moving, have a special "historical premium" to them).
4) that bitcoin's chain will even still be running in some or other form.
This is why the "last bitcoin" sounds to me rather the "last used bitcoin" (the last transaction). This can happen 2 years from now, 20 years from now, 2 centuries from now, whatever. It seems logical to me that the last transaction will be about 0 value.
You could even say that if bitcoin forks off into, say, a PoS coin, then the last true bitcoin has 0 value because it is on a dead chain (another chain continued, but the true bitcoin PoW chain may be dead at a certain point).
You could just as well ask what is the value of "the last Deutsch Mark". Well, it is zero (apart maybe for some collectors). Because there were still Deutsch Mark around when Germany switched to the Euro and after a while, declared Deutsch Marks not to be exchangeable any more for Euros. At that point, these Deutsch Marks became zero, but people mostly had converted their former Deutsch Mark into Euros. This is similar to a substantive hard fork where the original dies.