Roughly speaking a protocol is merely an agreed upon way of communication. It is neutral in the sense that the protocol is well defined
and you are free to implement code that is compliant with the protocol.
The unit price has absolutely nothing to do with this. In a system where you want to exchange ownership of something you need
to actually create that something. Either you put it all in at the start or you add it. To stick with the protocol concept.
Altcoins that are forks of bitcoin are merely modifications of the protocol where these aspects were changed.
And here we can see the difference. The bitcoin source code could be defined as an protocol. A neutral piece of software that you can use to build different applications on. But bitcoin(tm) itself is a speficic brand of service, that is only based on the protocol. When unit price is involved then it doesn't resemble anything else that has been called a protocol in the field of information technology.
It's like someone creating the IMAP protocol, and at the same time creating an IMAP using e-mail service and calling the service itself "the IMAP protocol"
I think you completely misunderstand what bitcoin as a protocol is.
You have units of account (bitcoins and fractions of bitcoins) that can be owned using public/private key encryption and a distributed ledger where probabilistic agreement is reached on transactions and new coin creation.
There is nothing that says what that bitcoin represents. The market is giving it a certain value but in itself it is merely a ledger of numeric values attributed to addresses that can be exchanged.
If everyone agreed that bitcoins represented beanie babies then that is what it would be.
What you are kind of arguing is that there should exist a meta protocol of which bitcoin is a particular implementation.
That is essentially a blueprint for arbitrary cryptocurrencies but you still would have to create specific implementations from it.
[edit] incorrect wording
Just because people give bitcoins a currency value does not mean that in essence it is NOT a protocol