Hi, I work in bridal, and I should tell you that most places are so busy at this time of year that they really don't have time to do alterations from other bridal shops. Some, like mine, also have a straight policy against it. But there are a lot of private tailors that are very good, but their prices vary, and it also depends on how much work needs to be done (hem, bustle, taking in/letting out, bust cups, etc). So they will likely have to see the dress on you first before they can quote you on the cost. Most places don't have standard alteration fees (Vera Wang salons being the only exception I can think of), but a good tailor is likely to cost at least a couple hundred dollars, but it's well worth it for the result. I would just suggest that if you can find a bridal salon that will do it for you, to start with them, but if not, call around and talk to a few tailors in your area, and find out if they have a lot of experience altering wedding gowns.