One common misconception that many people have is that each sportsbook is exactly the same. This is flat out wrong. Each sportsbook has a different way of setting the odds, meaning they will often not be priced the same.
In this example here, you can see how different the odds are from book to book, even though its for the same bet. A $100 bet on Betrivers pays out $220 in profit, vs only $190 in profit on Draftkings. Thats a $30 difference in profit between the two books!