"It is estimated that Australian same-sex couples would spend A$700 million on their weddings if they were allowed to marry, but now New Zealand will get a significant slice of money that should be spent here."
Couples already have publicly declared their intention to marry across the Tasman.
Expatriate New Zealand lesbians Lee Haukendahl and Kerryn Benefield said they would wed on September 21.
Emma Mansell said she would also marry her partner in New Zealand after a ceremony in Sydney.
Mr Croome said he expected a flood of others to follow, with Australian politicians unlikely to change their minds on the issue in the near future.
While federal laws give gay and lesbian de facto couples the same rights as heterosexual couples in superannuation, social security, health, aged care, taxation and employment, successive efforts to legalise same-sex marriages have failed.
Labor policy supports same-sex marriage and allows MPs a conscience vote, but Ms Gillard and other prominent MPs oppose the move.
Greens Senator Sarah Hanson-Young said her party's bill would legalise marriages performed in New Zealand.
"The sad thing is when they arrive back home, they are no longer going to be recognised," she said.
Read more: Gay couples rush to name the day