I am all for keeping costs down so here is what I do. I do my own hair, make-up and nails. There are a few very helpful videos on Youtube on how to do make-up. I only splurge for professionally done hair and make-up for the really big comps. I bought all my dresses from Asian dressmakers through Ebay. They cost about $200 each and were made to measure. This way I can have more than one. I find I can get sweaty and uncomfortable under the lights so if there is a couple of hours wait between individual dances and championships, I can change dresses.
Try rooming with another competitor if you are going out of town. I have roomed with my pro partner when It was only the two of us. I wasn't about to pay for two hotel rooms. Be up front with your studio and your pro about how much you feel comfortable spending. I have a limit. Know beforehand what kind of meals he eats, for example. Steak or burgers?
I do not pay for my pro partner's time because I pay for coaching for the both of us from a Champion dancer. So I have no studio or pro expenses except for entries, hotel, gas and meals. He is very good at keeping costs down. I get an exact accounting from him after every comp.
Not counting entries, dresses and shoes, I spend around $1000.00 for an out of town comp. Less than $100 for a local comp.
I love competing in the pro-am category but I am not going to be a blank check.