What's the "real value" of a movie? The cost of making the movie?

Your argument seems to imply that a movie would never make any more (or less) than the cost of producing the movie. This is obviously not true.

Just because electricity and hardware costs were involved in producing bitcoins, doesn't mean bitcoins will retain that value, just as putting money to produce a movie doesn't guarantee people will pay to watch it.

Similarly, just as movies might have make more value than was put in when producing it, bitcoin could do the same.

Perhaps at some point in the future, there will be a paradigm shift and people will really value decentralization. At that time, a decentralized cryptocurrency (or a number of them) will be used as the main currencies of trade. Then the cryptocurrencies must have value equivalent of a few trillions of USD current value.

Perhaps bitcoin will gain some sort of collector's value in the future. Or become the main currency used in black markets, which again, would give it extra value.

What you said may sound logical to you, but really it's quite flawed. It may be that bitcoin never goes over $300 USD again. But there are any number of scenarios in which it would go past $300.