Where do people print personalized items sold on Etsy & Ebay?

Hi! I see a lot of products that you can buy cheaply on Etsy.com and Ebay.com that are personalized with initials, or names or what ever. For example, I found a “store” on Etsy.com where you could buy a designed mouse pad personalized with your initials for $9.95. Do they use a service for that that they resell? Zazzle.com and CafePress.com are WAY more expensive for a one off. How do they do it? Where do they do it? Do they have their own equipment? Personalized stuff can’t be a volume deal, can it? Thanks!