1 On average, a smaller conference room that is less 800 square feet will cost $50 to $250 for the half day. 2  Full-day rental for this type of space can cost upwards of $350 to $500. 3  Larger hotel conference rooms, such as a ball room or banquet center, can cost upwards of $400 to $1,500 per day. The cost of a hotel conference room will depend on the geographical location, the size of the room, and the amount of time you need it for. 2  On average, a smaller conference room that is less 800 square feet will cost $50 to $250 for the half day.