I don't know; that isn't terribly expensive for a convertible, it doesn't look too bad, sure it needs a bit of work, but considering an Impala of the same year would go for almost double this in this condition, this isn't an altogether bad deal.
Are you serious $16 K for a 70 LeSabre convertible? You can near mint convertibles in that territory. Please be around sometime I pick up a rat to flip.
That's looks like it has a fresh coat of "Resale Red" all over it. Rear valance wasn't even repaired before painting it. Looks sketchy from here.