The vig multiplier effect compounds with each leg. A three-team parlay pays approximately +596, but the true odds are 12.5%, corresponding to +700. A four-team parlay pays approximately +1228, but the true odds are 6.25%, corresponding to +1500. The longer the parlay, the larger the gap between the payout and the true odds. The sportsbook's edge increases exponentially with each leg.
The reason parlays are so popular is that they offer the possibility of a large payout from a small stake. A $10 parlay can return $50 or more. The dopamine hit of a parlay win is disproportionate to the stake, which makes the bet feel more exciting than a single wager. Sportsbooks design their parlay marketing around this excitement, not around the mathematical reality.
The mathematical reality is that parlays are negative EV bets even when the individual legs are positive EV. A bettor who consistently finds 5% edges on individual bets will lose money on parlays of those same bets because the vig multiplication erases the edge. The only way parlays are profitable is if the individual legs have edges large enough to overcome the combined vig, which is extremely rare.
The practical approach is to treat parlays as entertainment, not as a strategy. If you enjoy parlays, keep the stakes small relative to your bankroll and accept that the vig is the price of entertainment. If your goal is long-term profit, bet singles exclusively. The math is unambiguous: single bets are the only way to express an edge without paying the parlay tax.