So recently Firebase started charging for Cloud Functions container storage: https://firebase.google.com/pricing
No free usage $0.026/GB
I have deployed 2 functions several times (no more than 10 times, can't remember exact count, but this is still pretty low, IMO). Now I am already billed a small amount (fractions of a cent for now). So seems that if I deploy the functions another few dozens of times, I'll get close to a dollar, because old (and unused) containers are not deleted from the storage bucket.
Is there a way to safely delete outdated, not used containers to free some space? Well, it may seem that a few cents are not worth the time, but still, that's not what a free tier should be like.