With more than 40,000 people expected to turn out for the 20th anniversary of Pride March in St Kilda on Sunday, Midsumma organisers called on Melbourne's lesbian, gay, bisexual, transgender (LGBT) community to "put their hands in their pockets".

More than 100,000 flocked to Midsumma Carnival on January 18 in Alexandra Gardens, but Midsumma organisers told Fairfax Media the donations collected on the day amounted to just $15,000, a third of which went to support sporting groups who collected the money.

Although attendance at Carnival is free, Midsumma – a non-profit organisation run largely by volunteers – encouraged visitors to donate a gold coin to support the event.

Midsumma chair Aaron Hockly said the "disappointing" donations were a fraction of the cost of running the event, which receives no state or federal government funding.

Each year, Midsumma Carnival costs over $300,000 to run, including staging, security, sound, lighting, toilets, cleaners and licensing fees, while performers volunteer their time.

Roughly a third of the budget is covered by the City of Melbourne, but the organisers still relied on donations, bar sales and corporate sponsorship, he said.

"Everyone giving a gold coin donation would fund a third of the event, which is what we expect."

While some patrons donated "tens of thousands" to Midsumma annually and many donated $50 or $20 each year, Mr Hockly said a lot of people "gave nothing at all".

Two years ago, Midsumma was on the brink of collapse due to back-to-back losses and had to cut costs to survive.

Mr Hockly said many LGBT people did not how expensive the event was to run, or that the event relied on donations.

"There is an apathy and a general expectation that [Carnival] will always be there," he said.

Mr Hockly said he believed the declining donations reflected a wider decline in "public spiritedness" in the broader community.

While Carnival's immediate future is safe, Mr Hockly said if donations continued to remain low it would affect the longer term viability of the event, especially if rainy weather hit profits in future years.

"People need to realise that funds aren't unlimited, and if they want it to continue they need to support it," he said.

Midsumma will also be responsible for managing the annual Pride March held this Sunday for the first time, after the Pride March Association last year folded amid financial difficulties.

Port Phillip mayor Amanda Stevens on Wednesday said the council had nearly doubled its sponsorship to $75,000, up from $40,000 in 2014, to keep Pride March afloat.

The funding boast came after Midsumma told the council the event was "unsustainable", amid ever-increasing insurance, production costs and regulatory requirements, Mr Hockly said.

"It is a reality that the expense of running events [like] these go up every year."

While Pride would remain in St Kilda, Mr Hockly said the format may change in 2016.

"Pride March has to step up a level. Just walking down the street isn't enough anymore – especially for young people," he said.

Midsumma accept donations year round via midsumma.org.au