In Cryptocurrency Coins prices, the Coinmarketcap(cryptocurrency market analysis) gathers the data to each of every exchanges that they've recognized then sums up and gets it average so just like in Sportbet.io it also tracks the average data to which these odds in favor to, you can compare it to other sports betting that they've almost the same.
Manny Pacquiao is a more experienced boxer than Keith Thurman and he's a small favorite.
Sportsbet did it once for a promotion but they don't always track the average data from different sportsbooks to set their lines. As Botnake mentioned they have their own odds provider, other sportsbook have similar odds because they could be using the same provider but have lower margin on certain markets.
To me using the average data just makes sense, and as you'd expect the odds do vary from provider to provided which is why its important to look around before placing your bet. It's just a matter of being a little smart before throwing away money