Ten years into the Irish property boom, and it’s finally happened. We are no longer shocked by the €1m well-located semi. How about €2m for a plush two-bed bachelor pad? But of course.

But €10m or more for an ivy-clad Dublin trophy home? The answer to that, too, is a resounding “Why not?” These days, a well-placed Dublin estate agent could lean his elbow on a calculator, attach the resulting figure to a handsome house, and still we’d buy it.

Paul Murgatroyd, an economist with Douglas Newman Good, who has been keeping an eye on the sales figures of the very upper echelons of the Irish property market, says the number of homes selling above the €5m mark is relatively tiny, but, importantly, the figures are growing.

“Just a few years ago, you would have seen only one €5m-plus property up for sale in a two-year period. It’s still a small number today, but now it is a growing portion of the market.”

According to Murgatroyd’s auction-based figures, not one home managed to command the golden €5m figure back in 2002. The only house to warrant the slightest gasp of surprise back then was Glenmore House in Clonee, Dublin 15, set on 121 acres, which was sold by Lisney for €4.1m in October that year.

In 2003, two houses topped the €5m mark. Argyle House and No 31 St Mary’s Road, both in Dublin 4, earned their vendors €5.1m apiece. Argyle House jumped almost €1m above its guide price, while St Mary’s made a mockery of its €3.3m asking price.

This year, for vendors things are looking up — way up. To the end of September, about 1% of houses sold at auction in Ireland raised more than €5m. A fairly insignificant proportion this may seem, until you do the maths: nearly seven times more houses have topped the €5m mark (15 houses out of 1,200) than two years earlier. And that percentage applies only to homes sold at auction. Mammoth price tags are just as likely to be found in private-treaty sales today.

Clontra in Shankill, Co Dublin, is the starkest current example. The 19th-century gothic manor house sits on 19 acres overlooking Killiney Bay. Though the sale includes a separate two-storey detached residence, a cut-stone stable yard and a gate lodge, the private-treaty price tag is still a stonker: €18.5m.

It’s practically going for a song, though, compared with Walford. Set on uppity Shrewsbury Road in Dublin 4 — a guide-price-accident black spot — the seven-bedroom Edwardian redbrick went under the hammer at €35m and came out the other end having relieved its new owner of €58m.

In the broadest terms, this represents €8m more than the estimated cost of overhauling the entire Leaving Certificate system in Ireland, and roughly the same amount that the Irish public donated to the Asian tsunami disaster fund.

But Walford, at least, could defend its priciness with a reasonable excuse — its 1.8 acres of garden had enough room to add five new addresses, potentially, to Shrewsbury Road. Although the sale attracted widespread coverage in the national press, the public it seems, no longer chokes on its cornflakes while reading about property prices in the Sunday supplements.

But whatever we learn about A-list properties in the newspapers, it’s behind closed doors that the real money changes hands.

According to Denis Beare at Lisney, half of the Dublin housing stock worth more than €5m is never advertised or publicly viewed and never makes it onto the auction result pages. Last year, a five-bedroom home in Temple Road, Dartry, Dublin, was snapped up by Michael Whelan, the wealthy developer, for €10m in a would-be secret sale, ultimately outed to the newspapers.

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