Was free for as long as I've known it existed. Telerik recently bought by 'Progress' (ironic), software re-written in Electron and now charges a subscription to use it.
Glad HTTP Toolkit is now available free for 'hobbyist' tasks - https://httptoolkit.tech/
I should mention here: not only is the core product all free, it's also completely open source, even including the paid bits (https://github.com/httptoolkit). And those Pro features are completely free for all contributors to the project.
I've tried to set it up so I couldn't run off with it and force everybody to start paying even if I wanted to, but any suggestions for further improvements there very welcome.
I was very, very impressed when I opened the Android mode and my Genymotion emulator just opened automatically with the VPN app and connected.