The entire scene is, mutatis mutandis , surprisingly "British"-looking. Britain did have some brief involvement in that part of the Indies before the Dutch took over. As far as I know, back home in Europe the Dutch had no tradition of this sort of thing by the date in question. Today, neither do the Indonesians themselves (except recently in Aceh, see below), unlike their Malaysian, Singaporean and Bruneian neighbours, who have so enthusiastically embraced the CP system bequeathed by their former colonial masters.
If not money, then what? For starters, Marte goes out in front of an audience of hundreds of thousands every day and tries not to fail in front of them. He runs out of the dugout with a team of friends that he tries not to let down. He plays a sport that will record everything he did and wave it in front of him for the 50 years or so he lives after his retirement. People cheat at golf, at crossword puzzles, at Sporcle quizzes, at card games with their family members. Half the bats in a Sunday slow-pitch league are illegally doctored . So of course there's incentive for ballplayers to cheat when the world is poised to GIF their every failure.
There are certain standards for proof that must be met in Islamic law for zina punishment to apply. In the Shafii, Hanbali, and Hanafi law schools Rajm (public stoning) or lashing is imposed for religiously prohibited sex only if the crime is proven, either by four male adults witnessing at first hand the actual sexual intercourse at the same time or by self-confession.  For the establishment of adultery, four male Muslim witnesses must have seen the act in its most intimate details. Shia Islam allows substitution of one male Muslim with two female Muslims, but requires that at least one of the witnesses be a male. The Sunni Maliki school of law consider pregnancy in an unmarried woman as sufficient evidence of zina , unless there is evidence of rape or compulsion.   However, the punishment can be averted by a number of legal "semblances" ( shubuhat ), such as existence of an invalid marriage contract or possibility that the conception predates a divorce.  The majority Maliki opinion theoretically allowed for a pregnancy lasting up to seven years, indicating a concern of the jurists to shield women from the charge of zina and to protect children from the stigma of illegitimacy.  These requirements made zina virtually impossible to prove in practice.