SailOrion might be right, but I'm not sure. I'm wondering if there's an opportunity to negotiate with some charter cos or the peeps over at sailonline? Especially if you waited until May to book. I think some owners have something called "short notice time" (or some similar phrase) that you can get at an even deeper discount?
Also, if charter co's have a boat at the dock that's not going out, but is available, they might be willing to move on price (everything is negotiable, right?). It could take some effort, but this could pay off if you could save $500 to a grand off the lowest available listed price.