It depends on several things; The weight The destination The origin The type of transport The class it is sent
The current rate is 44 cents for an ordinary letter.
Effective May 11, 2009 the cost is $0.44Since May of 2009 the postage for a standard size and shape of envelope weighing one ounce of less is 44 cents.
from america, about 2 dollars if its moderately light.
It all depends on where you are mailing your letter from. The price always changes, but it's never expensive.