Verified answer

They might charge you something like $5 if it was an old fashioned metal key, but the plastic key cards are very inexpensive and they won't care. I doubt they're worth more than a nickel.

Hotels will usually tell you that there is a charge for replacing a key to prevent you from loosing them; however, they usually won't if they are just the plastic type. They would probably only charge you if the door lock itself had to be changed for some reason.

Well they gave you 3 obviously they expected you to lose 1