いくらis used to give the quantitative measurement of certain things.It is generally ised while asking about the price of an commodity(nedan wa ikura desu ka?).
#4816 "I don't know how much this motorcycle is" should be "I don't know how much this motorcycle would cost."
fixed, but not sure if the english was wrong to start with really...
Just a note to say that いくらか is a completely diferent word meaning "a relatively small amount."
いくらか得したの = Did you make some gain? いくら得したの = HOw much gain did you make?
I'm not sure it's wrong per se, but it is bad English because it's unclear when stated alone. In a known context it would be fine, but alone it could mean anything like, "I don't know how much this motorcycle is loved."
...and I concur with bamboo4 that いくらか means "some," and could be confusing Japanese to a non-native speaker, but in this case and in this context it clearly means "how much?"