So i sell mainly trading cards and charge shipping on my items. Most fall into the ebay standard envelope and i charge the .69 cents. I run promotions and frequently get buys of 4 items and i typically then ship usps which costs like 4.50. Ive run into a few buyers wanting much more cards and always just refunded the excess shipping they end up paying. My question is, is there a way to set a cap on the shipping charged? Say someone buys 20 cards under 20 dollars, instead of being charged 13.80 for shipping could i run a cap at 5 so they only get a 5 dollar charge? I fell like i would get more bulk buyers this way even though i do always refund the shipping difference if they pay more. Any ways to do this or advice is much appreciated! I didnt want to run free shipping and bake the cost in though i am considering it now.