I always do what dhbookds suggested and that is once I have the shipping address I look at the various options available and may change the method of shipment without changing the class.

I have used it several times and Pirate Ship's rates are close to the same as the eBay discounted rate. You can then upload the tracking information into the order.

There is another option called priority mail cubic which is good for smaller heavy packages up to 20 pounds but you have to use another shipper like Pirate Ship to purchase and print the label since eBay does not offer it.

Flat rate is always cheaper for very heavy items and I have shipped 50+ pounds of lead a couple of times in a medium and/or large flat rate box. Weight 20 lbs.As others mentioned there is no way to tell where the break even point is due to size, weight and zones. weight 4 lbs.), or Medium and Large Flat Rate Boxes (Max. Weight 70 lbs), Flat Rate Envelopes or Small Flat Rate Boxes (Max. Priority Mail International pricing varies by country price group, either in packages charged by weight (Max. For all other GXG items, prices based on dimensional weight or actual weight, whichever is greater, and country price group. Prices for items mailed in USPS-produced GXG envelopes based on weight and country price group. weight 4 lbs.) Back ^ to legal disclaimer 10ġ1. Weight 70 lbs) or Flat Rate Envelopes (Max. Priority Mail Express International pricing varies by country price group, either in packages charged by weight (Max. Visit the International Mail Manual for Priority Mail International insurance details. Not available for Priority Mail International Flat Rate Envelopes or Small Flat Rate Boxes. Visit the International Mail Manual for Priority Mail Express International insurance details. Limitations may apply for certain destinations. Actual number of days may vary based on origin, destination, and customs delays. You must pay postage and mail your letter or package at a Post Office™ location. You can receive date-certain service with a money-back guarantee to select locations. See Publication 141 for more information on insurance. See Publication 141: Global Express Guaranteed Service Guide for more detailed information. See Publication 141 for more information.

Usps large flat rate boxes prices