For instance, at Yahoo, the same games are listed like this. . .
Favorite Line Underdog Line
at St. Louis -250 San Diego 220
at Atlanta -130 Houston 120
That makes sense for what I posted earlier.
The reason that there’s a “30 cent” difference for the STL game and a “10 cent” difference for the ATL game is a little complicated.
If you care, the easiest way to explain it is by an example.
Let’s say teams are evenly matched, and your bookie gives you a “10 cent line”
-105
-105
(you need to bet 105 to win 100).
If you play that 10 times, betting $105 each time. 5 times you’re expected to win $100 and 5 times you’re expected to lose $105, so you’re out $25. That’s the same no matter which team you pick.
Now, let’s say a team was a 9-1 favorite. If they did “10 cent lines”, the odds would be
+895
-905
If you bet the favorite in that (at $905), 9 times you can expect to win 100. 1 times you lose $905.
If you bet the underdog in that on average: 9 times you would lose $100, and one time you would win $895.
That means that out of 10 bets, the bookie has only won $5.
So, when the odds get more skewed, the books build more juice into them. Sometimes for a fight, you’ll see odds like +500/-700.