There are several confirmed fixed match instances in cricket, so it's very real.
...How much are they hoping to get from a sports book that they don't make as a league or club
In match fixes cases I have heard, it's always some criminals who approach players (never heard of sportsbook) to fix games and regarding money, man's thirst for money is endless, and if one is getting paid well for little 'effort' (sure, the potential for disastrous consequences is there) then they may decide to do it.