The bookmakers set their odds to make a profit whatever the outcome, the odds are based on money expected to be placed and statistical probability. Many OLBG member create their own betting odds before the bookies have priced up an event, it's a very worthwhile exercise and should become part of your betting life.
Pari-mutuel and fixed odds betting on horse racing and football are legal under Hong Kong's Gambling Ordinance, but all bets must be placed through the Hong Kong Jockey Club (HKJC). However, many locals use Hong Kong betting sites powered by international bookies as they offer better bonuses and odds.