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.
That's not how sportsbooks work.
I agree, I believe sportsbook has odds provider and they just follow it, IMO, not all sportsbook has the same odds provider that's why we see in some sportsbook that they have more betting lines and odds, usually big sportsbook have the best odds provider.