The CSO give average earnings as €45, 111which times 6.69 gives €301,792, which strikes me as a little more than the actual figure, although I find sale price data hard to locate.
The index seems to use the following: "net disposable family income, as defined as 1.5 * the average net salary (50% is assumed percentage of women in the workforce)"
These comparisons are always hazardous. Is average net salary for full-time workers or both full-time and part-time workers? Is it the mean or median? Is it from surveys of households or employers?