What is my EV for this type of wager?

[tech49]

I once made the following wager at a Jai Lai fronton. There was a daily double wager. There were two matches with 8 players each. I placed $10.00 on every combination of 1,2,3 and 4 (Match one) and all 8 numbers for Match 2. I had a 50% chance of losing all of my money, and a 50% chance of winning some money. Within the second possibility there was a chance that I would win less than I had wagered.

As It turned out, one of my numbers won in match 1 and I was lucky and ended up winning more than I wagered. I know that this was mathematically unsound. I want to know exactly how unsound?

Exactly what is my EV for this type of wager?

In addition, If one of my numbers wins in match one, what are the combined odds that have to be paid out for each match in order for me to break even.

Thanks

[Siegmund]

Jai Alai frontons are usually pari-mutuel betting. That is, the payoffs on each proposition are in proportion to how much money was bet on each of the possible outcomes, with the house taking a fixed percentage of the betting pool.

The percentage will usually be fixed by state law. I don't live in a state where such betting is allowed, but my recollection is that 15% is typical.