BridesmaidAid.com to the rescue!!!

4. How much is this gonna cost me?

Being a bridesmaid is more than just a time commitment, it's a financial one as well. One magazine reported that the average bridesmaid spends close to $900 per wedding, but your actual costs will vary a great deal.
Typically you'll have to pay for:

Gifts: engagement, shower, wedding.
All of your travel expenses.
The bridesmaid dress and any alterations.
Shoes and having them dyed to match the dress.
Stockings, underwear, bras, etc. . . .
Having your hair and nails done.