The three companies shared €600,000 between them from the last two shows alone. There have been 18 editions of the programme to date.
The €600,000 has been earned from the one million votes cast at an average cost of 60c per text message or phone call during the last two shows.
Teenage fans and parents have also bought over €107,000 worth of tickets, 7,000 in all, for the seven You're a Star shows filmed at the Helix Centre in Dublin City University.
"We're very happy with the success of the programme but the deal is commercially sensitive," said Padraig Leahy of RTÉ Commercial Enterprises.
The producers of the show, independent company ShinAwil Productions, are paid a commission by RTÉ and do not share in the call revenue.
You're a Star has earned increased audiences for RTÉ, with more than 650,000 viewers for last Sunday's show. It is expecting even more for the final two shows, which will decide who represents Ireland in the Eurovision Song Contest.
The man who commissioned the programme for RTÉ admits he is surprised by its success. "It's exceeded my expectations. But Irish people like good entertainment and we're blessed that we have so many talented performers in this country," said Kevin Linehan.
More than 5,000 people took part in auditions at venues around the country and the three judges selected 72 performers to go through to the televised shows.
Voting was initially slow, with an average of 50,000 votes per show, but it has climbed to 500,000.
"It's grown out of all proportions compared to similar shows in Britain and Europe. There are ten times as many people voting per head of population compared to other countries," Mr Linehan said.
The increase led to numerous complaints from viewers that they were paying for votes which were not being counted. In response, RTÉ changed the announcement of the winner from Sunday night to Monday morning to allow more time to process the votes.
O2, the sponsors of You're a Star, said part of the show's success was due to tribal voting with viewers backing contestants from their own counties. The show is a particular hit with young teenage girls.
O2 sponsorship manager Mark Lee said the Eurovision was also a factor. "People like to have their say in who will represent them. And it's a family affair everyone from 12 to 60 is watching," he said.
Michael Leonard from Fermanagh, Mickey Harte from Donegal and Simon Casey from Offaly will compete for the Eurovision spot on the next episode of You're a Star on Sunday at 8pm on RTÉ1. The final will be held on Saturday, March 8.