To stop this issue as you are selling all Brand new items, register your account correctly that is, as a Business Account, then you won't have this excess postage issue, you can select your own.
You are on a Private account, this is for those selling their unwanted used items, say a garage , attic or wardrobe clear out. Private sellers have to use Simple Delivery, and your items are not exempt so subject to that higher priced postage.
Change your account as below , you won't be on Simple Delivery and importantly, you'll be registered correctly...
- Go to Account settings in My eBay.
- Select Personal information.
- Select Edit next to Account type. You may be asked to sign in again.
- Select Confirm to upgrade to a Business account.
- Specify whether you operate your business as a legal entity or as a sole proprietor and select Continue.
- On the following page, enter your business information such as name, contact information, and returns policy. Then select Save.
Probably best to use a PC / laptop for this, and not the app or mobile browser. Chrome seems to work best on eBay.
@clint13