In reality, if it was slammed this low (on bags) you'll find that the car either has a serious amount of tuck, or massively modified arches, or both (see rusty
)
As for comparing them to the stock rims (which I assume are 17/18 inchers):
Obviously this isn't 100% fair as the overlayed image has the wheels right up in the arches, but I'd say that's maybe an inch difference. But even so, they still look a bit like 12/13's, which is probably a bit small - what's the harm with enlarging those arches a bit anyway?