JCP has been good for prom and homecoming dresses. Occasionally, we've had luck at Sears. We've gotten good deals on prom dresses at David's Bridal. We've picked up dresses when they are off season and on sale. Dd got a gorgeous gown at JCP for $39 on clearance that she ended up wearing to the prom. One of the benefits of that approach is that the kid is less likely to encounter other people wearing the same dress. I just picked up a beautiful gown from Kohl's for dd that somebody ordered online and returned that they gave me 80% off, plus I had a coupon. It came to just under $21!
My kids also tried on the idea that you could never wear the same dress twice, but I shut that down pretty quickly.
They are also free to swap with similarly sized friends, if that works.
I hate Deb with a passion.
This past prom season, it seemed to me that there were lots fewer dresses in the stores (JCP, Sears, Boscov's, Macys) than in past years, and I saw the same dozen dresses over and over. I hope that trend doesn't continue.
My kids also tried on the idea that you could never wear the same dress twice, but I shut that down pretty quickly.

I hate Deb with a passion.
This past prom season, it seemed to me that there were lots fewer dresses in the stores (JCP, Sears, Boscov's, Macys) than in past years, and I saw the same dozen dresses over and over. I hope that trend doesn't continue.