Compared to an average 6 pack of nice beer, which is about $10. Yes, there are some upfront costs, like a decent set of pitchers and some staple liquor. Suck it up, you're an adult now, right? And per drink, boozy punches are cheaper.
People don't remember a party for having tons of cheap beer; they do remember an event with a themed and delicious drink menu. A well thought out signature drink makes you look like you have your shit together. Bonus points for punny names.