Gonna write more on this but short answer is that developers time isn't free. If using React SPHO saves literally one hour in all the time you're using it (could be years) vs these other alternatives then you're already ahead.

And I tried to design it so that it saves you and your team a lot more than an hour.

I would pay if I found the library better than the free alternatives. Specifically, I would pay if the library allowed me to reach my goals faster: simple, well-designed, not doing too many things and well documented and maintained are the key factors.

One reason for paying is to ensure that the library is maintained: too many people out there assume that labor is free.

I would not pay for anything that isn't open source, though, because I do not want to become fully dependent on something that might disappear.

Because OP has an incentive to continue supporting his library