Taxi licence holders are raking in tens of thousands of dollars each year by renting out their plates while drivers earn a pittance, figures from the Taxi Industry Inquiry have revealed.

The average cost of a taxi licence in Melbourne has sky-rocketed in the past decade to $500,000, double the price paid in the early 2000s.

Licences in Dandenong recently sold for more than $400,000 and more than $300,000 in Ballarat.

Most licence holders have nothing to do with providing taxis, instead renting their rights out to operators who pay about $30,000 a year, while the value of licences also soars.

Meanwhile, drivers are earning as little as $8 an hour, according to the Victorian Taxi Association.