@benebox
I generally dislike parlays in any sport, whether MMA or tennis. I also need to correct one basic assumption you're making.
Not true at all. In fact, tennis is more high-variance than MMA. A player ranked 100th in the world beats the 30th best player all the time. It's a very tricky and somewhat random sport.
Now, there are a FEW players in the entire world, whether on the women's or men's side, who have an amazing degree of consistency. Djokovic, one of the greatest players ever, is one.
Dominic Thiem, who you included in a few parlays, is another.
But even someone like Medvedev, a ridiculously talented player who pushed Nadal to the absolute limit at the US Open Finals last year, ranked number 5in the world, isn't quite consistent enough to put in such a massive parlay, especially at those odds.
He is 3-3 in his last 6 tour matches, with losses to Agut (12th in the world), an ancient Simon (58th in the world), and a fringe player like Pospisil (104th in the world).
To use a MMA example, imagine Dan Hooker or Charles Oliveira losing to Evan Dunham. That's the equivalent of losing to Pospisil, and yet, that's not especially unusual in the tennis world.