An online platform recently accepted our merchandise to be sold on their website. I would have to ship cartons of merchandise from our warehouse to their designated warehouses. For small parcels, I'm thinking UPS, FedEx, and the likes. If I purchase shipping labels directly from them, I would probably get charged retail price which is the most expensive. How to get the best deal from shipping cartons (weight under 50 lbs) in the US? I'm not sure about the volumes yet but I'm guessing around 10 cartons per month to start. Please advise. Thank you.