What does this mean? Many people have the impression that there are a bunch of sports experts in Las Vegas who know the likelihood of different outcomes of a contest, and use their expertise to "set" odds that somehow reflect an objective fact about the world. But what really happens is this:
"By adjusting the odds in their favour or by having a point spread, bookmakers will aim to guarantee a profit by achieving a 'balanced book', either by getting an equal number of bets for each outcome or (when they are offering odds) by getting the amounts wagered on each outcome to reflect the odds."
If the bookmaker can equalize the dollar amount to be paid out when Murphy wins and when Callahan wins, and then can take a commission or vigorish from that, the business is guaranteed to make money, no matter the outcome of the event.
So picture a contest between some hypothetical Callahan and some imaginary Murphy for "Lightweight intellectual champion of the world." It just so happens that for every dollar bet on Murphy, 19 are bet on Callahan. Let's say there were only 20 $1 bets, to make our math simple. The bookmaker has $20 in his pocket. He wants some of that left there when the contest is over. So he sets the odds 19 to 1 in favor of Callahan. If Callahan wins, he pays out something like $1.04 for every one dollar bet, and is left with a quarter in his pocket. If Murphy wins, he pays out $19.75 to the single Murphy better, and is left with a quarter in his pocket. The bookmaker wins either way!
So the bookmaker has no interest at all in anything that might be called the "real" odds in the contest. His odds are simply the odds that balance his book, and guarantee he will make money whoever wins. If he personally believes that Murphy is being seriously underrated in this contest, he may make a bet himself on Murphy. But then, of course, he is acting as a bettor, and not a bookmaker.