The US Post Office - Cheapest in the World (almost)

Cost of a First Class Stamp
Greece0.82
Italy0.82
New Zealand0.8
Austria0.75
Germany0.75
Ireland0.75
Great Britain0.72
Iceland0.63
Netherlands0.63
Czeck Republic0.58
Canada0.57
Australia0.55
USA0.45
Israel0.42
USD
Sources: ilsr.org