Sorry, Crystal. Unfortunately, that is the way that it is with fiberglass
trailers. We have had members who question the worth of a trailer, because the blue book shows them lower but those numbers are not right. The demand for these trailers drives their worth. A reasonable trailer (which may not be quite the right price according to blue book) is usually snapped up.
You might want to spend some time looking at mods on this web site while you try to find another trailer. While I do not remember any that increase the sleeping capacity of a trailer as many of us have raised our children, there might be some mods that could be adapted.