There are all sorts of games the seller can play. Since the total payback is 50% they don't need a huge incentive to cheat but.... Think about what you would do if you were the seller and 75% of the spaces were already sold and the biggest prize was still hidden. If it were me I would just throw the rest of the board away and bank my profit.

If anyone wants some punchboards I have 5 or 10 different old ones for sale from $10-15 each. The biggest problem is the postage on them is significant. If interested email me at chipnut@comcast.net and I can send some photos.