Maybe eBay are charging you listing fees? A breakdown of fees / postage taken is shown in your Payments>> Summary >> All transactions here:
https://www.ebay.co.uk/sh/fin/transactions
You are selling all Brand New items, so you should be registered as a Business seller. A Private seller the one you are using , is for selling second hand, used items, say a garage / attic / wardrobe clear out.
This will show you how to change your account to the correct one.
- 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.
@bargainbloomuk