It sounds like you booked at the first possible moment. Ticket prices 330 days out are usually pretty high because UA (I presume) assumes that anyone booking that far in advance really wants to lock in their trip and is willing to pay a premium. I booked my Island Hopper visit as a RT originating in EWR, with the longest non-Hopper legs in F/J, and the whole itinerary was closer to 7.5k all in or so. That was for December, so call it a little under 9 months out.