LocalStack is a third party that has a free and paid version of their product. I'm certainly NOT against anyone trying to make a living off of their own hard work but, Google provides their emulator free of charge. Supposedly this can drive greater adoption.
GCP emulators cover only a very small portion of their services though. AWS also has emulators for some services they provide free of charge. LocalStack adds more than just emulation though, it has a bunch of developer tools that enables local cloud dev much more broadly.
