I want to return them, not just exchange. As the boots are heavy, $40 -- the amount you suggested -- won't be sufficient to cover the shipping cost. Please consider paying at least $65. I hope to hear from you soon.
Then, I would like you to return the item instead of exchanging items. Because the boots are heavy, additional $40 will be needed even when you choose the cheapest shipment method. I want you to absorb at least $65. I hope your prompt response.