That is reasonable but it might also be more than Amazon's willing to bear. It costs money to handle cash and it's more work to stock and flush these machines. Amazon may have a business case for these stores that depends on paying the relatively small merchant fee to credit card networks and knowing that they don't have any burden of handling any cash.
AFAIK these stores employ security/loss-prevention (and stockers as well, just not cashiers). There’s people at the door in the videos I saw. How do they stop people from stealing?
The article is clickbait.