It's not an "unfunded mandate". It's funded out of the tax receipts.
So Texas will keep 20% of their NST receipts as a administrative fee to cover the cost of collection, but Massachussets will keep 85% because they have a bigger bureaucracy and need to pay more government salaries. Who will audit them? Who will check that their admin costs are correct? What if they don't pay?
I think the part he was referring to would be the costs of collection.