How do you go about pricing?

I recently went to a meet and greet and owners were aware of the price for 2 dogs. As I was leaving, the owner then said, Oh, can you feed the outdoor cat twice a day, the aquarium fish once a day, and the hermit crabs once a day. When you are basing your prices do you allow for additional duties or is it taken for granted that it all comes with the original price? While the additional requests weren't anything big, I felt they were trying to do it underhanded as I was leaving the home.