No, you will not receive extra money from us for a device in a sealed box. In fact, we open the sealed box because we test all devices. It is our promise to the potential buyer of your device that we have thoroughly tested and inspected the device.
Therefore, if you do not agree with our final price offer after our assessment of your device and want it returned, we will send your device back to you in the original box but unsealed.
On some platforms where you sell directly to the buyer (such as Facebook Marketplace or Vinted), you might get more for your device if you sell it in a sealed box, so consider this carefully beforehand.