Clinical IQ tests are administered by psychologists and created by publishers. Pearsons WISC-IV Basic Kit costs $1,123.40.

It's a bit like brand-name drugs and generics, except that the generics aren't allowed to copy the exact chemical structure of the brand name drug in a similar way that research substances copy controlled substances with minor chemical alterations, with unknown effects.

Now these free online IQ tests could create their own IQ test, but that requires both expertise in creating IQ tests, and a large normative sample (WISC used a normative sample of 2,200 children between 6 and 16).

Furthermore, creating more accurate IQ tests does nothing for their bottom line, or may even hurt it as some of these tests are biased to give you higher scores, so that you may share them on social media.

Whilst you could invest in creating an accurate IQ test to be cheaply taken online, you'd have to fight the perception these less accurate tests have created that online IQ tests are about as accurate as horoscopes.

As an interesting note, pearson does offer computer based IQ tests under their Q interactive brand, however, they are not cheap.