What does the price of anything mean?
Why is a Audi "worth" $60K but a VW "worth" $30K? A Porsche "worth" over $100K? Why is a Patek Philippe or A. Lange & Söhne Tourbillon watch worth $100K? Why should I pay $300 for one All-Clad pan when for the same price I can get a 10-piece set at Costco?
Surely you have things that you think are worth paying more for while for others you wouldn't spend more than some 'basic' amount.
People perceive things as being of different quality.
It's not that everyone (!) thinks that GameStop (GME) is "worth" over $300 a share, it's just that the folks at the hedge funds are willing to pay over $300 for each share because they have contractual obligations to fulfill, and if they do not they (a) may be sued for a lot of money and/or (b) go to jail.
So each share of GameStop is "worth" this much to the hedge funds because it gets them out of paying the consequences of (a) and (b). Paying $300/share may be "cheap" compared to paying those consequences.
And to go back to my first paragraph: a Porsche is not "worth" $100K to me—because I'm not willing to pay for it, or even for an Audi. But it may be "worth" it to someone else because they are willing to pay for it.