To add euro symbol, i make a setting in :

Regional and language -> Keyboard Layout -> Advanced -> Adding EuroSign to certain key et I check E (Clic to enlarge) :

Then, click on Apply.
If you open kwrite, ant you type ALTGR E, it should work.
In Konsole, you have to set view -> Character Encoding -> Western European -> Iso 8859-15

to be sure that the symbol work.