A December 2013 price is about £0.88, but you should check with your local post office, as these prices change and there are other factors, such as how fast you want it to be delivered.
That depends on where in the world you are sending it from, which you have not stated. If you go to your local post office they will give you the current prices.
60c-90c
Cheap
For a standard letter it is €0.82 although if you want to send something larger the costs would of course increase.
what does a ordinary stamp cost to souther Ireland
It all depends on the price of postage
Where from?
US$0.98
The cost of air mailing a letter from Australia to Ireland is $2.60. A registered letter is about $22.00. It takes three to ten days for the transit.
$50
0.98
From where?
€2