If you wager $100 cash on odds of +100, you are staking $100 cash to win $100 cash. Your total potential return is $200, which is your initial stake plus your winnings. If you wager $100 free play on +100, however, your total potential return is just the $100 winnings. Whether you win or lose, your free play is used up. Obviously, free play bonuses aren't worth as much as cash bonuses, so that means it's up to you to squeeze as much value out of them as possible.
To show how this can be exploited, take a point spread of -8.5 at odds of -110. This is a 50/50 proposition. Let's assume you've purchased enough points to move the spread to -6.5 at odds of -150. Now, you'd win instead of lose 6.24% of the time they win by 8, and 6.59% of the time they win by 7. Add these together with the 50% from the original proposition, and we get 62.83%.
The -110 on either side is like paying a tax or commission to the sportsbook. Bettors would pay 10 percent (aka juice) to the sportsbook, which is essentially a fee for brokering the wager. So, the -110 indicates that a bettor must risk $110 to win $100. Some sportsbooks will even reduce the juice for you which means you can earn the same $100 payout but risk less money to do it.
Had you initially bet $100 on the Mavericks, you would walk away with a profit of $90.91. Now, if you bet on the Mavericks, you will see a profit of only $76.92. On the other side of the bet, an earlier bet on the Magic would have paid you $105. Now that same $100 bet will get you $125 if the Magic win the game. Ideally, this will entice more people to bet on the Magic and the action on the Mavericks to slow down.
Earlier, we explained how the implied probability of -240 is 70.59% and how the implied probability of +210 is 32.36%. Notice these two probabilities total 102.95%. The extra 2.95% is the bookmaker's advantage. It's called vig, and it's basically a commission that they charge customers for placing wagers. By removing the vig, you can see what the fair odds on the game would be.
Two possibilities existed for Seahawks backers at this point – either the team would win the game by at least three points or not. There was no possibility for a push, thanks to the use of a half-point. It’s impossible to score a half-point in football, so thanks to the magic of rounding, there’s no room for a tie outcome. Those who backed the Patriots were looking at two possible outcomes, too – either New England would pull off the upset or they would lose by just a point or two. Both would turn out in a win.
Let’s take a quick step back and talk about what the sportsbook’s goal is with any game they are offering action on. Ideally, the sportsbook wants to take the perfect amount of action (money bet) on each side of a game so that regardless of who wins, they make money. Their profit comes from taking a small percentage off of the top as a house fee for facilitating the action.
With NFL odds the over/under can vary but usually it’s somewhere between 35 and 47 points. Let’s say in the Colts and Bengals game that the total is posted at 37.5. If Indy scores 27 and Cincy gets 13 points, the total would be at 40 and the over would win. But if the Colts rack up 35, and they shut out the Bengals, the total of 35 would be under.
Oftentimes you’ll see a point spread that has a half-point added to the number. Of course, there’s no such thing as half a point in a football game, so why do we so often see point spreads with a (.5) attached to the score? Sportsbooks do this to make sure there isn’t a chance of a push. Let’s take another look at our game from above with the half point added.