Question

mysterious customer: i heard you might bake the best muffins in the land. would you accept this magic mirror in exchange for some?
snidely (annoyed) what do you mean i might bake the best muffins?
mysterious customer: well..., i asked the mirror to direct me to the best chef in the land. but it couldnt decide between you and chef bertha.
snidely (anxious) bertha? seriously? give me that mirror, ill ask it myself
mysterious customer: only the mirrors owner may ask the questions. ill
what does snidelys response to the mysterious customer tell you about him?
snidely does not like to talk to new customers.
snidely does not believe in magic mirrors.
snidely is greedy and cares only about money.
snidely has a very high opinion of himself.

Explanation:

Snidely's annoyance at being told he "might" bake the best muffins (implying uncertainty about his top - chef status) and his eagerness to prove himself (by wanting to ask the mirror directly, likely to confirm his superiority) shows he has a high self - opinion. There is no indication in the text that he dislikes new customers (he is responding to the customer), no mention of his disbelief in magic mirrors (he wants to use it), and no focus on money (the exchange is for muffins and a mirror, not money).

Answer:

Snidely has a very high opinion of himself.