Each independent Artist sets the price of the printed products they sell. That's why some masks can be more expensive than others. Added to that are taxes and cost for shipping. Head over here to get more information about pricing on Redbubble.
Since artists control the price of their products and receive the profits from their sales, each purchase you make helps support them and their creative work.
If you want to purchase masks for friends and family, there is a bundle discount of 20% off when you buy four or more masks.