The developers at Objective Development are offering Little Snitch 4 for 50% off normal prices. This includes single or multi licenses as well as upgrades from prior versions. (This software is for macOS only.)
Single License $22.50 (normally $45)
Single License Upgrade $12.50 (normally $25)
etc.
https://www.obdev.at/products/lit…order.htm
This sale usually only happens once a year, and normally lasts only 1 day.