Well I think usually it's not even about the risk/return money wise. The psychology of it is probably even stranger than we think. I think to a lot of E-sports players who threw games for almost nothing and were banned for life. Or even Clase, the small kickbacks he got wouldn't have even covered the future salary loss.
I think what more often happens is it's done for the thrill of getting away with it. Or it's done as a sort of 'favor' to friends/family. That is, it's more of an emotional thing when done than rational. And so giving harsher punishments has some deterrant but less than we might think.
But I also think as MLB gets more in bed with gambling sites, the potential for really big scandals occurring is increasing. We think of this from a player perspective, but the people who run gambling sites get tempted too. It might not even take a whole company being in on it. Again, it's not rational but this is how it goes.
Would be an interesting FanGraphs article. Were there more post-season games than pure odds would dictate? Doesn't seem like it would be hard to calculate out.