Charters for less than 1 week...YES
I know that Go Native Yacht Charters in Miami will send a boat out for "broken" weeks. We went down for 2.5 days and chartered their Fountaine Pajot Venezia 42. Of course, as you said, price-wise, they made it worth their while, but hey, thay''re business people too! Also, they offer a 10% return customer discount which is nice. great people, too. Really enjoyed the experience.