I didn't go to my high school prom, and have no regrets whatsoever. With my looks and social skills being exponentially worse than they are now, plus not having a car (a guy had to have a car in order to date in my school), finding a prom date was out of the question. If I could lower my standards (I didn't start doing that until college), I probably would be able to get a date, but oh well. Then again, here's how the costs would break down for my school, at least under the traditional "guy pays for everything" model.
Limo ---------------- $100/hr * 3hrs = $300
Tuxedo ------------- $100 rental = $100
Prom tickets ------- $ 60 * 2 = $120
Pre-prom Dinner -- $130 (for 2) = $130
After-prom Party -- $ 50 = $ 50
Grooming ------------ $100 = $100
Flowers/Corsage -- $ 50 = $ 50
Total Damage = $850
For the girl, the cost is generally limited to the dress and spa treatments. Not sure how those break down, but definitely much less than the guy's expenses, with the total being only a few hundred dollars. Plus you got the Glass Slipper Project charity, which provides girls with used prom dresses at no charge! (No equivalent exists for guys, so they have to pay for tuxedos regardless of their economic situation.)
As you can see, the cost/benefit ratio for attending prom is infinitesimally small. First of all, all the popular people will definitely be there, and will use the last remaining chance to pick on me. Two, knowing my pick-up skills, I'd be lucky if I get more than a hug and/or a kiss on the cheek from my date. Three, back in high school, I couldn't dance well even if someone held an AK-47 to my head, which means I'd embarrass myself. And all that for $850? No thanks!