The USPS has recently increased the rates based on volume. This has unfortunately caused problems with the shipping cost estimator in certain cases, mostly in lightweight products in larger sizes than 12" x 12". Our policy will be to see if we can ship by an alternative method at no additional cost to the buyer. Otherwise, we will request additional payment to cover the additional cost or give the buyer the option to cancel the order. We are investigating ways to fix the shipping cost estimator.