The purpose here is to explain the value of bitcoin, using a normal commodity as a starting point, and deriving the value of bitcoin from that.
A precondition is agreement of the theory of demand and supply. This is basically that value comes from the considerations of people in their minds and their actions, each person has a stepped curve of value per unit, and these demand and supply curves are aggregated on the market.
Take a commodity that is produced and consumed, and is durable (so it is possible to hold), like aluminum or copper.
There are only two types of actors in this model of the market, the producers and the consumers. Both the producers and the consumers can hold, the producers after it is produced, and the consumers before it is consumed. So the producers and consumers meet on the market with their supply and demand curves, where the curves cross, trade happens, and after the initial trades, more trades occur only when the curves change. The commodity moves like this:
Production -> store -> market -> store -> consumption
Obviously, when production parameters change, the supply curve changes, and some will be sold on the market. The same goes for the other side, when the stuff is consumed , the consumers take to the market to buy more. The equilibrium price changes accordingly.
When the price is low, the producer might increase his store, this can be called reservation demand. When price is high, more will be produced. Conversely, when the price is high, consumption goes down, and the consumer might turn seller by reducing their holding.
Now to money. The special thing with money (fiat or bitcoin, gold is a bit of both, money and consumable commodity) is that money is not consumed. Think of consumption as destruction of the goods for a purpose. When you consumed a candle, it was destroyed, but you got the light that you wanted. There is no reason to consume money by destroying them, it gives you nothing, (compared to what you get when you trade them).
On the other end, production, bitcoin is not produced either, after the initial amount is created. (Fiat is special, since more is continually printed, but they don't have to be).
So what we have left is this picture (producers are not producers any more, but sellers, and consumers are not consumers any more, but buyers).
Seller -> market -> buyer.
Since a seller can not sell more when he is empty, he also has to buy, to continue to be an actor. And the buyer can not buy more than he has other goods or services (or other money types) to sell, and he doesn't want to either, because he can not consume the money. Therefore we can combine the buyer and the seller:
Seller/buyer -> market -> seller/buyer
And they have to change roles sometimes, so
Seller/buyer <-> market <-> seller/buyer.
Conclusion: The value is from the demand and supply, where demand comes from the wish to hold, and the supply comes from the wish hold less.
Thats all, folks. That is all there is to it.