"I said it should be based on some criteria, as in square footage, location, amenities, working plumbing, etc, not on a landlord’s whim."

It's already based on all of those criteria, which is why rents in certain parts of the city are higher than others, and why rents for larger units in the same part of the city are higher than rents for smaller units.  A landlord can whim all they want to charge $10k/month, but they won't get it.  Who gets to set the rent price on a privately-owned piece of property, if not the owner?