As soon as you print over 10 t-shirts screen printing becomes both lower cost (a t-shirt that starts at $15 on Spreadshirt can be $6 on Teespring) and higher quality (digital printing produces less vibrant colors and washes out much quicker).

Short version: Teespring allows you to produce higher quality products at a lower price point. We also add the benefit of game mechanics and make the experience more social.