I had a $99 dress from a place similar to David's Bridal (it cost another $100 for alterations -- they took the skirt off and "raised it" to make it shorter while preserving the ruffles around the bottom). It was PERFECT. Admittedly, this was 22 years ago.
A non-financial lesson: Suggest to your daughter that she listen to other people's opinions. I went into the first dress shop knowing EXACTLY what I wanted. I wanted something very simple, white satin, cathedral train. I tried on this dress, and I was very happy with it -- ready to buy it. My mom pulled another dress off the rack and insisted that it was better. Just to make her happy, I tried it on . . . and, oh, was my mom right! It was NOTHING I said I wanted. Well, it started with white satin . . . but it was 100% lace over that white satin, and it was topped with pearls and sequins. The skirt was layers and layers of ruffles, and the train was short. But it suited me soooo much better than what I'd chosen based upon magazine pictures. Once I tried on the "right dress", I realized that "more was more" and the long-long train I'd wanted was too much for my short frame.
Back when I was buying my dress, people used to say that you should plan to spend the equivalent of one year's clothing expenses on your wedding dress. I thought that was crazy-high then, and I think it's crazy-high now. You have to find a balance between "this is the only wedding I'll ever have" and "I'm going to wear this dress once".