If you go to the PA lottery website, there's a More tab all the way to the right. If you select About Us & News from the More tab, you can get to a profit report. In glancing through that report, total sales on Fast Play for previous year was $149 million. Overall, they are returning a 20% payout margin, so going from that Fast Play brings them roughly $120 million a year. They keep around 80 cents on every dollar the players spend.
In June 2024, they are mandated to roll the payout percentage back up to 25% and you can tell by the way that section is worded, they're not exactly happy about that. I'm sure the politicians push them hard to earn more. Act 97 in 2019 allowed them to roll the payouts down to 20%, but that Act expires in 2024. If you've wondered why the scratchers have gotten so much stingier with payoffs, that's why.
As far as what happens to the jackpots baked into the games that expire, those jackpots technically didn't exist. The payouts on Fast Play appear to be designed to wait until the hopper is full before paying off so the payouts can never get ahead of the money coming in. Any monies left over after a game ends just gets folded into the profits.