If it was an intentional bet then it was incredibly stupid - depending on how much of a drop in price you are willing to accept the maximum bet you can place on TAB is in the range of 1%-3% of the pool (so between $200-$600 for a $20000 pool). Anything more than that and you are just cutting your own throat.

The other possibility is that it was an accident and either the TAB, agent or punter has had to wear the loss. When I worked at the TAB there were a few similar cases (none for that amount!). Basically when punter places a bet they sometimes mark the ticket incorrectly or the ticket gets misread which can result in bet being incorrect (eg. $1000 instead of $10) - the agent must then cancel the ticket and reenter it - but if the race jumps before they can do this (if ticket was scanned just before the jump for example) they cannot cancel the ticket themselves and must ring the TAB head office. In the case of Supertab if the TAB is not Victoria then the TAB head office must ring Tabcorp and ask them to cancel the bet - but this can not be done once the race has finished. In the case of a greyhound race (or if there is a delay in any of the phone calls) it may not be possible to get the cancellation done in time which means the bet stands and someone has to pay (unless it wins!). Usually that is the punter if the ticket was filled out incorrectly, the TAB if the error was caused by a scanning problem or the agent if it was an agents error.

I bet the people who backed the winner where happy - gave them an extra couple of dollars on the div that they weren't expecting!

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"Computers can do that????" - Homer Simpson