This includes the remainder of this season and all of next season, playoffs included.
Bear in mind that there have only been 24 such occurances in the history of the game, the most recent just yesterday (6/28/23). That said, there were 6 between 2009-2012.
There have been 7 perfect games in the last 20 years, and we're a bit over halfway through the season, so I would at first have put the odds at about 3/20 = 15%, which is a little higher than where I found them. But when I looked at the dates of those 7 games, all but one were in May and June. So I'm speculating that perfect games are harder to achieve late in the season (due to weather, tired pitchers, etc.) and considering the odds to be more like 5%.
I like these types of markets that require you to follow the entire league and hopefully remember that you're in this market when you get into the 7th or 8th inning of said potential perfect game to pump the hell out of the YES bet.
Only for DJ LeMahieu or some shit to bobble a ground ball with one out in the 9th to wreck the whole damn thing.