Amazon seems to be really fluctuating their prices recently. They had the Frigate for $83 a couple of weeks ago, then it went back up to full retail, then back to $83, then back up again. The Police Station did a similar thing recently too and I snagged both on their second "dip" after regretting not taking advantage the first time. So it wouldn't surprise me if the price of the Frigate goes down on Amazon again within the next week or so. I noticed even some of the new Star Wars sets had pretty good discounts on them yesterday.
it looks like amazon sold out of their inventory as the default seller for the frigate is now a third party. i doubt it'll come back to the store since the set is slated to be discontinued if it hasn't already.