Unfortunately I can't afford a custom made dress. I wish it were an option!
The place I'm hoping would dye my dress had dyed a couple of wedding dresses and they've gotten good results according to the reviews on YELP. I'm not worried about their ability to do the job.
As for having 'the' dress, it's my senior prom and I want to wear something I like. Formal attire is required, so why waste money on a prom dress I'd feel stupid in when I could buy a dress I love? This is the last time I'll be wearing any kind of formal gown for a while so I want to enjoy it.