It's still what their spend is and it has limits. I'm comparing the 1B to what they have to spend. Why is your GDP number a more accurate representation?
Let me repeat again that $1B is a lot of money and, of course, should be put to the best possible and efficient use. I think that we agree on this one.
In the context of Texas, $1B is not that much money. From your stated $359B Texan total state expenditure, the $1B is less than 0.00279%, so pretty minor, and even much smaller when compared to the Texan economy of $2.4
trillion by GDP, which makes
Texas the 9th largest economy in the world by GDP.
Any increase in taxes to finance that $1B is easy to do with very little impact on the economy. I'm not even sure you can measure the impact reliably, but here economists have to chime in (real ones, not the political hacks).
Now, $1B is for sure a huge deal for a number of smaller (in GDP) US states, like Vermont with a GDP of $40.6B, never mind their state budget. For them $1B would be a burden, but for Texas, not at all.
So perhaps this better explains why I wrote that $1B is a "rounding error" in the context of the Texas economy?
en.wikipedia.org