I can't see anyone from the SCA referring to something they wanted to commission as a "princess gown." For starters, the word "gown" refers to a type of clothing which is on the very tail end of what would be considered "period," so you won't see it often in the SCA (the greater the span of history in which something appeared, the more often you see it in the SCA). Secondly, gowns are generally intended to be worn in very clean indoor quarters, making them very impractical for outdoor events, and most SCA events are outdoors.
Lastly, Prince and Princess are titles that are
earned in the SCA (by winning a fighting tournament, in fact), and the people who end up in those positions do plenty more than play dress-up. Besides, most custom jobs are commissioned within the SCA, since major events usually have numerous clothing merchants present who specialize in SCA garb.
Anyway, pinkrandomattack, I'm glad to hear of another up-and-coming costumer, and I'd like to know more about what you do.
Do you have examples of previous costumes you've made, and about how much they would have cost if you were to make them again on commission? As I'm sure you know, different costumers vary in their rates of labor, and in the quality/expense of the materials they insist on using...
Also, how long does it usually take you to finish a costume (choose an example)?