Australians have wagered more than $100 million throughout Tabcorp outlets on the Melbourne Cup, won by local Vow And Declare.

But turnover was down 5.9 per cent on last year to $106 million, with total betting on the rest of Flemington's 10-race card also falling 1.5 per cent to $160.7 million.

NSW and Victoria punters collectively outlaid in $77.1 million in bets, a 6.9 per cent decline according to Tabcorp's managing director of wagering Adam Rytenskild.

The Melbourne Cup betting slump tracks with a recent downturn as the Caulfield Cup (down 25 per cent), Caulfield Guineas (down 14 per cent) and Turnbull Stakes (down 10 per cent) meetings all experienced drops this year.

"It should be noted that many factors influence racing turnover and turnover figures from a single race or meeting are not necessarily indicative of the broader wagering market," a TAB statement read.

UBET punters in Queensland, South Australia, Tasmania and Northern Territory also forked out almost $35 million.

Danny O'Brien-trained Vow And Declare opened at $51 on the TAB fixed odds but fell to a final starting price of $11.

One TAB punter was well ahead of the curve, placing $500 on Vow And Declare at $101 in June to collect $50,500.

Another NSW punter turned a $20 bet into a $56,497.40 return, picking the first four with TAB.

The TAB opened a fixed odds market for the 2020 Melbourne Cup on Tuesday, with Il Paradiso and Vow And Declare $18 joint favourites.