Interesting. But those figures don't really address the size of the respective tax bases, as the term is commonly understood.
The tax base for a taxing entity, of course, is how much taxable property there is within the boundaries of the jurisdiction. In this case, we'll compare the tax bases of the Houston ISD and the Austin ISD, using 2017 figures, which are found here:
Tax Rates and Levies
As you can see from the data, HISD's tax base is $2.029 billion, dwarfing that of AISD, at a mere $1.312 billion.
The reason AISD taxpayers end up paying into the Robin Hood fund to the extent the do, of course, is that their taxpayers are wildly overassessed and overtaxed relative to the number of students in the district. AISD had 83,000 (+/-) students enrolled in 2016, while HISD had roughly 215,000 (+/-) that same year. You can find that data here:
2016 Snapshot - 50,000 Student and Above
As AISD is a school district with almost no students, it would appear that AISD's contributions to the Robin Hood fund are attributable mostly to poor management and/or avarice on the part of AISD trustees, coupled with the general lack of awareness on the part of AISD property owners as to whether they are being overtaxed relative to the actual number of students in their district.
Anyway...I'm happy to have been of assistance in clearing up any misunderstanding on your part relating to the concept of tax bases. It was clear that you were having some trouble with the concept.
And by the way, if I were a taxpayer in Travis County, I'd be preparing to place some heads on pikes, after learning what I had this evening. No doubt you must feel the same way.