One of the standouts being the syndicate run by David Walsh (of MONA fame) and Zeljko Ranogajec. They made money because the rebates swung the odds in their favour [1].

My take is that: the syndicate wins because the odds were swung in their favour. The tote wins because even with the discounted percentage the increased pool size offset the rebate and made them more money. The rest of the mug punters lost since the syndicate was winning a portion of the pool they would have otherwise won. The rebates are a mechanism to reliably transfer additional money from mug punters to the tote via an enabling middleman (the syndicate).

[1] https://www.perthturftalk.com.au/discussion/discussion/11724...