They don't come cheap.

The six-figure salaries paid to the heads of major cultural institutions place them among Australia's highest income earners - higher in some cases than their political paymasters.

Art Gallery of NSW director Michael Brand earns $430,000 a year, while Sydney Opera House chief executive Louise Herron is paid $373,200. Both earn less than the $475,000 paid to Tony Ellwood, the director of the National Gallery of Victoria.

In comparison, NSW Premier Mike Baird is paid around $300,000, while the deputy premier and Arts Minister Troy Grant earns $270,000, according to the NSW parliamentary library. His federal colleague Senator Mitch Fifield, meanwhile, is paid just under $350,000.

A pay gap of nearly $165,000 or 38 per cent separates the male and female heads of the six major public cultural institutions in NSW plus the NGV and the National Gallery of Australia in Canberra, according to an analysis of executive salaries by Fairfax Media.

The median salary of the four female directors - Herron, Dolla Merrillees (Museum of Arts and Applied Science), Kim McKay (Australian Museum) and Elizabeth Ann Macgregor (Museum of Contemporary Art) - is around $270,000, according to figures collected from annual reports.

The median salary of the four male directors - Ellwood, Michael Brand (AGNSW), Alex Byrne (State Library of NSW) and Gerard Vaughan (NGA) is approximately $435,000.

In comparison, the 300 highest-earning Australian chief executives CEOs received an average pay packet of more than $3 million a year, according to The Australian Financial Review Salary Survey 2015.

The visitors to the four institutions with male directors totalled 4.8 million, compared with 3.5 million for the four museums headed by women.

Brand was unavailable to comment, but spokeswoman Simone Bird said the gallery was "committed to the NSW public sector's initiative of advancing women in the sector".

The salary figures suggest the gender pay gap at the top of the arts is much greater than for the overall workforce.

Australian men earn an average of 18 per cent more than women, according to OECD figures for 22 countries – one of the largest gender pay gaps and far worse than New Zealand, which has a 5.6 per cent gap.

Asked if it was fair for women in charge of major cultural institutions to be paid less than their male counterparts, Kim McKay said: "No, it's not fair."

"I'm a great believer you should get equal pay for equal work," McKay told Fairfax Media last year.

But she added: "I took the job at the money that was offered because I wanted to do it."

McKay said she hoped revisions to the employment system for executives would lead to "a more equitable remuneration program across all of the cultural institutions".

Professor Sara Charlesworth, from RMIT University's School of Management, said a lack of transparency in how salaries are determined widens the gender pay gap.

Performance-based pay also tends to favour men, who are paid larger bonuses than women in both the private and public sector.

Associate Professor Joanna Mendelssohn, from UNSW Art & Design, said: "They all negotiate individual contracts and none of them have small egos. Women are usually so thrilled to be actually asked they forget to negotiate the salary."

Mendelssohn also noted the state's major galleries and museums had become more reliant on non-government funding. Meanwhile, the boards of directors are stacked with members from the corporate sector.

"If you've got a board of trustees of rich men, they're going to assume that anybody who's worth being on the board with them is going to be paid a lot of money and is also more likely to be male," she said.

But Mendelssohn said the task of heading up a major cultural institution was "all-encompassing".

"It's a really hard profession to have a life," she said. "Any good gallery director is going to be out every night."

However, she highlighted the large disparity between the incomes of management and staff at these institutions.

"They're paid much more than their staff and that differentiation is quite shocking," she said.

"Australian executives are very good at saying how they've got to be paid as much as people overseas and end up being paid more."

But Australian gallery and museum directors may be less well-remunerated compared to overseas colleagues.

On average, the base salaries of the eight chiefs of Australia's major cultural institutions are five times higher than the national median income for full-time workers ($70,700).

In the UK, the average base salary of directors Neil MacGregor (the recently retired head of the British Museum), Nicholas Serota (Tate) and Martin Roth (Victoria & Albert) is £164,000 ($A323,168) - around six times the median for full-time workers (£27,500 or $54,189).

These figures pale in comparison to the US, well-known for the enormous disparity between executive and worker pay across all sectors.

The average base salary of Thomas Campbell (The Metropolitan Museum of Art in New York),  Ellen Futter (American Museum of Natural History in New York), Glenn Lowry (Museum of Modern Art in New York) and former NGV director Timothy Potts (Getty Museum in Los Angeles) is more than $US775,000 ($A1.05m) - 18 times the median income of a US full-time worker ($US43,200 or $A58,647).

MCA director Elizabeth Ann Macgregor suggested women were less likely than men to ask for pay rises.

"Women still tend not to put themselves forward," she said. "They don't say I'm worth this."

She said, in the past, gallery directors such as Edmund Capon (AGNSW) had settled for lower salaries.

"They would never have put their hands up … There was a kind of gentlemanly thing. You worked in the arts, you didn't ask for a lot of money."

The arts sector would benefit from being paid "on a professional level", she added. "Unfortunately, money does tend to make people value you."

She declined to reveal her salary but said: "It's less than the Art Gallery [of NSW]. That I do know".

"I'm not very comfortable talking about this, as you can tell, but I do feel women don't put themselves forward for pay rises," she said. "Maybe I'll do it next year."