I am pretty sure there are many that think these shops can be done quickly. I do not think all CEO's are in tune with what it takes to be a mystery shopper. Those who were shoppers themselves yes, you are probably right but for the large companies those CEO's may never have shopped or it was long ago.
The CEO may have been a shopper in his day and worked himselve up....I think they should have an idea of pay, not specifically but generally. .