My personal opinion is that Valentine's Day is just a Hallmark Holiday. We usually get each other cards and sometimes my husband will bring home flowers or something, but we don't make a huge fuss over it. Anniversaries and birthdays are much bigger occasions to us than some random day the greeting card companies have decided is the day to ramp up expressions of affection.
All that said, though, your friend - on appearances, based on what you have told us - seems to care little for his wife's feelings. The fact of the matter is that Valentine's Day is important to some people, and his attitude is lacking in respect for what the day may mean to his wife. Beyond all that, she might consider it a slap in the face to have him bring home the half price chocolate the next day, as if she isn't worth full price chocolate to him.
It sends a message, and the message is not a loving one.