On the cheaper side on the spectrum but not quite as cheap as TripMode, there is Vallum: https://vallumfirewall.com

I've been using it for years and the only feature I miss is domain/subdomain blacklisting.

If there is no need for such a granular control of outgoing connections for any given application, there's also the no-cost and open-sourced LuLu: https://github.com/objective-see/LuLu