As more couples opt for cheaper weddings, charity stores are benefiting, with rising demand for pre-loved wedding dresses.

St Vincent de Paul and the Salvation Army report strong demand from brides-to-be who don't need something new for their big day.

Salvation Army Warilla store manager Karen Martin said the charity held a wedding expo yesterday to show getting married need not cost a fortune.

"We wanted to tell people who can't afford a big, fancy wedding that they can still have a beautiful day," Ms Martin said.

"We have a lot of donated bridal gowns ranging from $150 to $500, but in some cases the original price tags ran into thousands of dollars.

"The old days of smelly charity shops are changing, so it's nice to be able to show people what we have and also raise money for our services and support local businesses."

Ali Krzyszton was one of the brides-to-be trying on frocks for size at the St Vincent de Paul Society's Mascot store in preparation for her big day next May.

"We're having a destination wedding at Byron Bay, which adds to the cost, so saving money wherever we can would be a huge help," Ms Krzyszton said.

"I've tried to get lots of quotes on everything from the rings to the food; same goes for my dress.

"Grabbing a bargain would allow us to spend more on our honeymoon in Costa Rica, so it's definitely worthwhile having a look at these dresses."

The bridal industry turns over $3.7 billion a year according to the Australian Bureau of Statistics with more than 111,000 couples marrying annually.

The most expensive outlay is the reception and venues often charge more for weddings than other functions.

"There are people out there ready to take advantage of you, but a corporate function and wedding are two different functions and a wedding will often take more planning and there's a higher level of expectation, so some venues do charge more," Glenn Findlay from the Australian Bridal Service said.