Many of Ed McBain's 87th Precinct titles go on sale for $0.99 or $1.99 pretty often, but here are two for less than $0.99, which is much less common...
Killer’s Choice, #5, $0.24 (!!!! - I wish I didn't already have it, just so I could buy it for this price

)
Kindle US:
https://www.amazon.com/gp/product/B005WZZRQU/
Kindle US/Smile:
https://smile.amazon.com/gp/product/B005WZZRQU/
Fuzz, #22, $0.71
Kindle US:
https://www.amazon.com/dp/B07H14KJ36
Kindle US/Smile:
https://smile.amazon.com/dp/B07H14KJ36