nurbs files tend to get big cause of the tessalation and stuff..
it's not out of the ordinary skyeyez that it's that big.. i've got a scene i made of a garden and it's around 40mgs..
just to be sure though check in your outliner just incase you don't have anything double that you don't need.. if not, i wouldn't worry man..
btw.. i'm not sure about this.. but if in your scene you're workin' real size object.. meters instead of cm or inches, that will make the size bigger too (i think.. )