A 12x12x8 room will have about 384 square feet of wall space. 384' x $.70 = $270 (268.80) Paint for this room will run about $.20 per square foot of wall space. This will add about $70 to the price above if using a Benjamin Moore high quality paint.Then, sundries, or supplies will be added.They typical cost for this will be about $50 ($.13 per square foot) for a typical room.aint for this room will run about $.20 per square foot of wall space. This will add about $70 to the price above if using a Benjamin Moore high quality paint. Then, sundries, or supplies will be added. They typical cost for this will be about $50 ($.13 per square foot) for a typical room.