Several of leading potential suitors for the stations, including UTV and the Irish Times, were stunned by the 233m price tag outlined in an information memorandum circulated to buyers last week.

It is understood, however, that around half a dozen private equity firms have expressed interest in the stations, including Quadrangle, a US company that specialises in media investments.

One leading figure said that the "extremely frothy" valuation placed on the firm by Emap was an attempt to attract the attention of such private equity firms.

The most likely private equity suitor for the firm remains, however, TV3 owner, Doughty Hanson, which may feel able to achieve synergies between the station and Today FM.

"There's a strategic value there that might not exist for anyone else, " said one source.

Another source suggested that Emap may also be attempting to pitch the stations at media companies such as the Irish Times and Independent News & Media, which lack significant Irish radio interests.

"People who want to get into the market may be willing to pay over the top, " he said.

Industry sources have also said that Emap's calculations for the future earnings before interest, tax, depreciation and amortisation (EBITDA) of the group did not appear to take into account the potential effect that forthcoming regional youth licences could have on Today FM.

According to calculations, EBITDA at the stations will rise by 43% over the next three years from 11.6m in year to March 2007 to 16.7m in the year to March 2010.

"The BCI are dropping licences willy nilly at the moment. Most of their EBITDA comes from Today FM and it will be the biggest loser when these licences come in because it has a high youth audience, " said one observer.

Paul Moran, managing director of media buyer Mediaworks, also said that Today FM may face challenging times in the near future.

"With the new stations, Today FM will find it hard to maintain its share of the advertising cake, " he said.

He also said the consensus among media buyers was that, although this year would be very healthy in terms of advertising growth, "three or four years down the line, there will only be modest single-digit growth".

However, a source close to Emap insisted that the valuation placed on the stations was achievable and was based on the value of UK stock-market listed media groups.

Emap's 233m valuation of the stations is based on the assumption that their market value is 16 times their EBITDA, which is an unusually high multiple by Irish standards.

For instance, when the former owner of the stations, Scottish Radio Holdings bought Highland Radio in 2004, it paid the equivalent of 10 times the station's EBITDA, which worked out at around 7m.

The only media transaction involving a similarly high EBITDA multiple was the purchase of the Leinster Leader newspaper group by Johnston Press in 2005.

Johnston Press paid 17 times the group's EBITDA, or 140m in monetary terms.

However, many media sources believe Johnston Press paid too much for the titles, with some unsuccessful bidders later privately expressing their delight that their bids had failed.

Johnston Press's Irish titles have subsequently lagged behind the rest of the regional newspaper sector in terms of advertising growth and last month the company announced 71 job cuts across the group.

"The problem with calculating values based on EBITDA multiples is that they vary hugely between transactions so it's very hard to rationalise them accurately, " said one source.