USPS postage rates rise
June 1, 2015 - Postage rates increase today for both domestic and international mail. Most notably for CardShark users are increases in the costs of First-Class Mail Parcels, which is the class of mailing recommended for most card orders. In some cases, these rates have gone up close to 10%. This means shipping costs and seller reimbursements for postage on the site have increased all around.
Sellers, you may want to look at services like USPS click and ship and stamps.com, which provide some discounts on postage.