While Greece's minimum wage before the crisis reached about 700 € and now it got to just under the 600 €, Ireland's minimum wage was at 1200 € only to be cut in the current year for about 80 €. But if you go in any supermarket or any department store, the prices of the goods do not differ much.
I wouldn't put too much thought into minimal wages. Many European countries don't have any (including all Nordic countries, Germany, Austria, Switzerland and Italy). Those who do are quite arbitrary and do not necessarily reflect the cost of life or GDP per capita. According to Google's public data, here are the minimum monthly wages in the eurozone.
Luxembourg : €1,724.81 per month
Ireland : €1,461.85 per month
Belgium : €1,440.67 per month (or €1,387.5 under 21 years old)
Netherlands : €1,416 per month
UK : €1,169.49 per month
Greece : €862.82 per month
Spain : €738.85 per month
Slovenia : €734.15 per month
Portugal : €554.17 per month
Slovakia : €307.7 per month
Estonia : €278.02 per month
Life isn't more expensive in Ireland or Belgium than in the UK, yet the British government decided to set a fairly low minimum wage for its workers. Likewise Greece has a lower GDP per capita and considerably lower average salaries than Spain, yet the Greek minimum wage is higher.
And this is not just between Greece and Ireland. I have travelled in many European countries, mainly in the Eurozone, and the prices do not differ much; the wages though do. How can anyone justify that Europeans must be paid differently for doing exactly the same job? Why must an Irish that works in a check out in a super market earn more than a Greek, and a Greek more than a Slovakian one? Why since we have the same currency, and a common market, common prices for most goods we still have unequal wages? And not just the wages but our pensions too! An Irish pensioner is earning about 800 € per month, while a pensioner in Greece about 300 or 400 € at best.
The main explanation is that housing cost varies
a lot between countries like Ireland and Greece. Food and manufactured goods are part of a worldwide market and a global distribution network, which explains why the price of an iPhone, clothes in global chains, or breakfast cereals of a same brand won't vary much from one country to another. Local produce will vary more because of discrepancies in local wages. But in the end what drives salaries up is the price of real estate. That's why a job in London usually won't pay the same as a similar position in, say, Lancashire or Cornwall, even though its the same country.
Salaries are high in Ireland because nearly half of the country's population lives in Dublin's metropolitan area, where housing is very expensive. Greece is much more decentralised, with lots of people living in sparsely populated rural areas. Population density drives real prices up, which has for effect to increase wages. Salaries in Paris are often twice higher than in other parts of France. In Japan, Tokyoites enjoy nearly three times the GDP per capita of rural prefectures. Yet Parisians and Tokyoites spend so much money on accommodation that they often end up with less disposable income than people in smaller cities (unless they are willing to commute long hours to cheaper suburbs). It's not a matter or country, system or education; eventually a great deal of the wage gaps depend on population density and real estate.