FWIW, and more OT, I sell frequently on eBay, but almost never in auction format. I will use BIN with or without offers. When eBay shifted to profit on final value with essentially free listing it made no sense to me to continue the uncertainty of auction format. I know what margins I need to make an acceptable profit. If you have no cost basis in an item an auction may be ok, otherwise you are either under or overpriced.
eBays current returns policy is also onerous. eBay is becoming like amazon in that they will let a customer return an item for any reason. The seller generally can’t fight it. If your customer pays the shipping costs, you will have to credit the final value, refund the shipping costs and pay the return shipping if you want the item back.
I have sold electronics where the buyer removed components and returned the item as defective. eBay won’t do anything.
I now sell a lot of items with free shipping. I build the costs into the pricing. I pay FVF on the total and figure that into my margins. Whether or not I offer a guarantee, the customer always has to pay the return shipping before a refund is issued. Customers think twice if there is a hard return cost.
On eBay you have zero clarity on best-offers which, in my experience, range from 100% to 25%.