A true even money chance will likely be priced at -110 or an implied probability of 52.4% and although the winning odds are combined to calculate the returns, so is the bookmaker’s advantage, if the price is well made. There is also the sportsbooks’ juice to consider. There is little room for error - selecting two winners appears achievable, but those hoping for large returns must be flawless over a greater number of selections. However, as you would expect, there are downsides and sportsbooks would not offer such wagers if they were not profitable for them in the long run.
It also doesn’t require a large stake to potentially return a big win. They are a lottery style bet where the bettor can exercise a degree of skill and expertise, rather than relying entirely upon the randomness of how the lottery balls are chosen. The attraction of parlays is apparent: returns can be large, a 6-team parlay, each priced at -110 wins $474.13 of profit on a $10 stake and such wins receive lots of publicity and live long in the memory.
