YOU SAID:
How much will it cost because I have a party tomorrow
INTO JAPANESE
明日パーティーがあるのでいくらかかりますか
BACK INTO ENGLISH
I have a party tomorrow, how much will it cost?
INTO JAPANESE
明日パーティーがあるのですが、費用はいくらですか?
BACK INTO ENGLISH
I have a party tomorrow, how much will it cost?
You've done this before, haven't you.