fun answer: I hope so!
serious answer coming from someone who is still baffled by how much weddings cost: he might have no idea either... like zero clue whatsoever that it could easily run $10,000 without you even needing to go overboard.
i think he has SOME idea of wedding costs. my brother's wife comes from a family who just couldn't afford to help pay for the wedding. my brother and his now-wife handled a lot of the costs by themselves, but i know my parents helped with the venue and food. so i'm guessing he has at least a vague idea of some of the big costs. i'm guessing the stuff that he's unsure of is stuff like wedding dress, band, alcohol, and all of the "little" stuff that really adds up.