I don't want to hurt your feelings, but those vertical shaft models sell for $200-$300 all the time. I personally would not pay more than $200 for it. For $500-$700 a person can buy a pretty decent horizontal powered/shaft drive GT.
Plus what they cost new is kinda irrelevant. I think they quit making those in 91 or 92, so it is around 20 plus years old and only lost $225 of value.
In my opinion, that series of cub cadets,was the beginning of the big box store lawn mowers.