@Tarana has a nice post
here in the mystery thread, pointing out that (some, many, all, ???) Ed McBain titles are available at $1.99 for the Whispersync version if you own or buy the ebook. And, many Ed McBain titles go on sale for $0.99 somewhat often, and for $1.99 even a bit more often...
As @Tarana points out, there are two McBain titles currently at $0.99, which makes their Whispersync deals work out to be $2.98 total.
Shotgun
link:
https://www.amazon.com/gp/product/B005WZZR9M/
Cop Hater
link:
https://www.amazon.com/gp/product/B007MDDD52/