Ireland ranks as the 11th most expensive country to live in, just behind the United Kingdom, according to data compiled by Numbeo. Ireland has a Consumer Price Index of 92.09, meaning the cost of living here is just under 8 per cent less than in New York (CPI=100). This index takes account of all the main components of the cost of living, such as accommodation, utilities, groceries, eating out, clothing and transport.
Of course all things are relative, and your real cost of living will depend on your own personal lifestyle choices: such as where you choose to live (central Dublin obviously being the most expensive; where and how often you eat out; where you shop (Ireland offers a range of supermarkets from upmarket to discount, as in most European countries).
However, Ireland has a high per capita GDP and most ex-pats are on relatively high salaries so you should find the cost of living easily manageable.