Bring old and new customers in, and provide a fun, social and useful experience.
Have a separate room dedicated to the sale. Only allow a set number of people to go inside at a time. Next person can go in when another one comes out. People have to register in advance. People go inside in registration order. Each person has a time limit on the stay inside. They get a wristband that will beep when time is up. Payment for the goods happens inside.