Do the other offerings you're refering to use tailwind css?
In that case I'm also paying for continued development by the tailwind team, unlike the free offerings. I don't mind that free toolkits use tailwind, that's the beauty of the MIT license, but I do value paying something to the creators to ensure continued development. Especially if my business makes enough money from it.
I use PrimeVue, which offers it's components in Tailwind, Bootstrap, and their own CSS framework. They also offer all the components as figma files and provide actual documentation of each component unlike tailwinds 3 lines of comments for each component.
NB. I've paid for both tailwind UI and PrimeBlocks.
Also tailwind UI doesn't come with figma designs, whereas all the other free ones do.
You're just paying a brand tax here.