I can't imagine traveling with 9 other people, but I thought I might mention that if 10 of you do take advantage of group airfare, all of you don't have to fly originate in the same cities. The rules are that you all have to fly to the same city on the same date, and depart on the same date, but as long as you stick to the same airline, fly on the same days and all go to Madrid, you can take advantage of a group fare.

Don't forget to add on the tax, which would be in the range of $100 to $120 each.