It's not very expensive, all things considered. $299 for a single-user perpetual license (includes all future updates too) or about $1k for a team license[1].
If it saves you a bunch of time writing and maintaining the sort of components they are showing off, probably worth it?
Yeah I strongly emphasise with them getting their money - the only problem with headless components being behind a paid license is that you cannot build a design system on top of them and open source it.
*EDIT* prominent close button and closing on back navigation added (probably people will complain about hijackng the back button now)