Oke so those dresses After School is wearing for Happy Pledis are part of the H&M campaign "Lanvin <3 H&M". (If you are living in a cave:
http://en.wikipedia.org/wiki/Lanvin_(clothing))
Of course you should look at the price tag first before you decide whether you actually like the dress

Although all these dresses are around 149 euros. Not sure what that is in dollars but you do the math
EDIT: Lol, I can't even spell the word dress