If you ask for the upgrade when you arrive and it is available it varies from $50-$100 extra per night. If you book a club room online it usually is a full $100-$110 per night extra.
I have never been to US/IOA, so forgive me if this is common knowledge, but what exactly do you get with the "club"? I have a standard at RPR booked for 4 nights in March. Thanks!