The following clip completes the pharmacy scene. The pharmacist sells the medication, reassures the customer that the medication is correct, gives the customer cautionary advice (advice warning about possible dangers) and says goodbye.
The word "simplest" (superlative adjective) is used to show that the medicine prescribed is the most basic. (Simple is an adjective with two syllables (sim-ple) and therefore does not need to be preceded with 'most' in the superlative form.)
The pharmacist is rather sarcastic when saying that he can find the customer a medicine that is more expensive.
"More expensive" compares the price of the medicine prescribed to any other potential medicine that the customer may go out and purchase. (In this case a medicine that the pharmacist can purchase for the customer.) (Is this an overly complex explanation? Is the last sentence in brackets needed?)
An important note is that the pharmacist makes sure that the customer understands the condition, the medicine prescribed and all the advice and precautionary advice given, and says; "Just tell me if there's anything you don't understand and I'll explain it again." Remember, a customer must always leave a consultation with a FULL understanding of what has happened.