Of course woot has it’s own printers going and well just how do they know how many shirts to print out?
“Once the supply of shirts for that day’s design is gone, the main page displays a “Sold Out!” notice. What is so great about this site’s savvy supply-and-demand model is that it prompts Shirt.Woot lovers to flock to the site early (like at 12:01 a.m.) so that they can nab cool designs before they sell out. The site generally offers approximately 1,000 of its commissioned-design shirts for each day and about 1,250 of its visitor-designed garments. One shirt sold out in 18 minutes.
When shirts don’t sell out in 18 minutes, it requires a delicate balancing act of knowing when to keep the press going and when to tear it down to avoid printing too many unsold shirts. “We do this elaborate ‘Frogger’ business, jumping over and back, trying not to take a design off the press until it’s done,” Lewis says, referring to the classic video game. “When a shirt sells out, it helps, because you know exactly how many you need to print. If not, you have to wait. It’s a stressful situation.”
So they are trying to match the amount of shirts printed with demand. What is cool about this is the fact that after you purchase your shirt, it’s actually going to be a shirt that no one else can buy, unless they purchased it that day.
This insurances no extra inventory, which as we all know extra inventory is not profitable, but also can not enough be unprofitable.

Image via vonMonkey