I agree on the 13", that I know of, the 9" never came with a cast base with a underslung motor, and the 10" had a lighter base.
Around here its about a $750 lathe at best,if it runs good. Its definitely worn well on the ways, crummy toolpost, no steady or follow rest, not sure what if any other chucks or faceplate, tailstock centers or chuck included? all that could raise price.
These days 9" lathes bring much more that the bigger ones...this one cant be compared to the 9" or even the 10" for price.
I buy and sell machine tools on the side, so this is just my 2 cents...