My husband and I had a talk this weekend about the price of alterations and what actually goes into that price. I know, you are probably thinking...you guys have no life. The truth is, the conversation was sparked after I finally hemmed a pair of his pants. Although he lives with a seamstress, I often get to fixing his clothes last. It really doesn't take that long to hem a pair of pants, and that is just one of the factors seamstresses incorporate into their pricing. A few other factors include level of expertise, materials needed, and time constraints.
Most freelance seamstresses will charge you per hour, and factor that into what they are altering for you. For example, a good seamstress can hem a pair of pants in a half hour. She should charge $10 an hour, therefore, charge you $5. If you need if done in 10 minutes, expect the price to go up. A great seamstress will most likely charge $15 an hour and charge you $7-$10 for the pant hem. And she will probably finish it in 15 minutes. If either seamstress doesn't have the correct color thread to match the pant, there may be an extra cost added.
Gowns and any taking ins or taking outs take much longer and this price will mostly depend on how long it will take a seamstress to complete the project. For example, I just recently received an alteration where the gown's hem is a pillow hem. This is much different than just a rolled hem. In a pillow hem, I must detach the lining from the outter fabric. Only then can I begin the process, which will be followed by about 5-6 more steps. In a rolled hem, I simply measure, cut, and roll. This will take much less time, thus, I would charge much less than the pillow hem.
Basically speaking, it is hard to tell how difficult a project will be for a seamstress, but the more difficult the project, the more it will cost. If you also start throwing at short time constraints, expect the price to go up. So, make sure your seamstress knows her stuff. You will be able to to judge that by the quality of her work, and the price she charges you once the project is complete. That will aslo determine if she keeps your business :)