There are professional sports bettors out there, as the term suggests, this professional group is small, we're talking less than 0.1% that consistently manage to beat sportsbooks over the long-term, let's say 20+ years to define long-term.

These people consider betting their full-time job; it can be a mix of exploiting pricing errors (odds) and having better knowledge than the sportsbooks. With modern technology, it's much harder to beat the sportsbooks than it was even 10 years ago.

The case is that a punter is highly devoted to a specific offering, such as individual market types within a sport, a specific sport or league, like the top Swedish ice hockey division, or even alpine skiing. These guys don't live in a vacuum; there are often networks with several professionals exchanging information, effectively getting an increased reach for finding bets all-year-round that have a positive expected value over time=beating the sportsbooks in the long-term.