How much does an updo cost?

my parents are going away tonight and prom is tomorrow. I'm getting my hair done at a salon with my boyfriend's sister but I have no clue how much it's going to cost. one friend said they had their hair done in an updo and it cost 45 and another said...

they did and their's was 65.

if it might help to say, I have sort of thin hair and it's maybe 2 inches past my shoulders.
if anyone has any clue how much it'll be, could you let me know?

around 40

Depends what salon you go to! I would take around 70 and more if you can just to be on the safe side. It shouldn't be this much but you don't want to be caught out! Good luck! I hope you have fun!