Sourcebooks Casablanca, who publish Georgette Heyer in the US, used to have a “birthday sale”, when they would put all of her books on sale for a week or so, around the time of her birthday, August 16. This hasn’t happened for many years, at least that I’ve been aware of. But it seems as if we may be getting the sale again anyway, well in advance of her birthday – my eReaderIQ feed exploded with Heyer titles for $1.99 each today. And they usually cost a lot more.
I have no idea how long this will last, and I’m slammed at work, so can’t really check it out, but here are a couple of links that pull up many Heyer titles at $1.99. Keep in mind that in the US, several of her early books are now in the public domain (e.g. The Black Moth, These Old Shades, Beauvallet), and so multiple editions of those clutter up the search results. But if you have a missing Heyer book or two you’d like to find at a good price, now’s probably a good time to go looking 
. They’re not all on sale, but a whole bunch sure are.