We went to Marsh Harbor two years ago and will heading there soon. Both times, our flights were booked through credit card points, so choices were limited. Can't recall the prices from 2004, but prices this year were in the $500 from IND. Itinerary both times: Indy to Charlotte to West Palm to Marsh Harbor. The first 2 legs are USair and the last leg is Bahamasair.
One warning regarding Bahamasair: When we were leaving, we checked in and was informed that USair gave us the wrong papers. We needed some sort of pass. Since we didn't have it, we would have to buy a one way ticket to West Palm for an exorbitant amount of money. We protested and made the supervisor call USair to clarify this issue. This also happened to the girl ahead of us who had purchased her ticket on one of the online booking agents (orbitz, priceline, etc. - can't recall which one).
Evelyn