I am assuming that all computer players of this game have access to the algorithm which I have discovered. I am assuming that all computer players have figured out the simple formula which gives them the cheapest profitable odds to back or lay an outcome given the commission and the outcome's probability (thanks to one of your previous comments).

I am assuming that there will be punters who bite at the odds I provide. If there weren't, then the game would not be sustainable.

I came across a "betting guide" for sale for this game which claims to advise on bets based on the "trends" seen in the game. I don't know what this means, but it gives me hope that there are people out there willing to part with their money in my direction.

Failing that, the novelty was an interesting one, and it's all about the journey, dude!

To clarify, I'm not saying your assumptions are necessarily wrong, or that you shouldn't try to test them and see what happens.

I'm just proposing another possibility is that everyone playing on both sides is a "punter" having fun (or deceiving themselves). In any case, that everyone is losing long-term. With 5% vig I'd guess that's the most likely possibility.

You might be right. Also if Betfair has its own bots playing as another commenter claims, then it will be hard to compete on odds. Only one way to find out.

Here is my guess:

45% of players don’t play well enough to win, even at even odds. Kind of mini-Dunning Krueger. They’re hoping for luck, and love to tell stories to their friends when they win.

30% are degenerate gamblers.

The balance play well enough that the loss rate is sufficiently slow so as to pay for the entertainment value.