My fiancée is exactly the same! He buys fancy $15 condiments cause he thinks they look good, and always always falls for multibuys on things we don't eat- he brought home 3 fancy organic 9-seed loaves this week cause they were buy 2, get one free.
A) they cost $12, as opposed to my normal $2 bread.
B) we eat about 6 slices combined in a week, so 2.5 loaves went mouldy
c) DS thinks seeds in bread look like ants and won't eat them.
I refuse to let him come grocery shopping, as he can manage to slip a few "good bargains" or "new treats" into the trolley, which inevitably makes the grocery bill cost $80 more than it normally does when I shop alone.