Why the Model Avoids Parlays
Parlays compound the vig: a four-leg parlay of -110 legs carries roughly a 20% house edge, about four times a single bet. Here is why that happens, why correlation makes it worse, and why Fairline sticks to straight bets.
A parlay combines several bets into one ticket where every leg has to win. The payout is larger, and so is the catch: the house edge compounds with each leg, which is why the model never recommends them.
The vig stacks
Each leg of a parlay carries its own vig. Combine them and the margins multiply rather than add. A four-leg parlay of -110 legs carries roughly a 20% house edge, about four times the cut on a single -110 bet. The longer the parlay, the worse the math.
Books price parlays as if the legs were independent and fairly priced. They are usually neither. The advertised payout is smaller than a fair combination of the same legs would pay, and that shortfall is the stacked margin.
Correlation makes it worse
Many popular parlay legs are correlated (a team’s moneyline and the game going over, for instance), and books still price them as independent, which tilts the edge further toward the house on exactly the combinations bettors like most.
Fairline focuses on single straight bets, so every play on the dashboard is a standalone wager with its own price, edge, and stake. If two of them win on the same night, that is two won bets, with none of the stacked margin a parlay would carry.