RK Bridal

They have a large selection of dresses - just make sure you read all the details of the 'no frills' program they have. I didn't get my girls dresses there, but I think that basically the dress is cheaper if you measure your girls and let RK know what sizes to purchase. No liability is on them if the dresses don't fit. They'll give you a paper explaining everything when you get there.

You can also have them measure the girls as would happen in a normal bridal store, but the dresses just cost a little more. And I think with the no frills they don't do alterations there.

It's true that they don't do the alterations...my friend was in a wedding party and got her BM dress from there. 2 of my work friends ordered their BM dresses and got them for under $120..
Just be very precise with writing down the correct model numbers, and color #.
Also it's better (and more cost effective) to do the alterations on your own..
If anybody needs a good seamstress, I have one for you!
The place is on Nassau Blvd in Garden City South and it's called Georgia's (or Georgia's tailoring??)
Georgia is an older Greek woman and she's great. She took in a dress for me and everything was perfect. She understands tailoring for different body types too, my friend who I recommended go to her (who got the dress from RK) is quite heavy, and Georgia fit it perfect to her body and also made it very flattering.
Good luck!