I don't get too worked up over buying/selling blinds. But, if the state really wanted to stop it, I think it would be the easiest thing in the world to stop. Have a TWRA officer from another county (or a sheriff's deputy, or an intern, or anyone they choose) hang out with the crowd. The TWRA officer running the draw pulls the first card but calls out a number that was intentionally left out of the barrel. The plain clothes officer yells and waives with excitement and starts towards the stage slowly, listening carefully to each offer he receives. When he gets to the stage, on-duty officers walk up and put handcuffs on everybody that offered to buy the blind. Then the head officer announces "everyone was warned that it is illegal to buy, sell, or offer to buy or sell these blinds. We are going to enforce the law."
He could then read out the real first number and there would be exactly zero offers made to the lucky winner.
Or, they could just nuke the whole system and replace it with a computer draw, 4-tier hybrid system of year-long/agency-built/blindless spot/boat hunt locations that nobody likes or asked for.