If there is a less expensive First-Class Mail option available, it is not set as the default. (This is a bug and we are waiting for a fix.)
On rare occasions, you may be able to place a product into your online cart, and learn it is out-of-stock during the checkout process. Our quantity on hand is only updated once the purchase is complete. Occasionally, we may run out of a specific product before you complete your purchase. We apologize in advance if this happens to you.