"Probably fees from previous sales e.g. Postage from previous sales taken out"

I'm sure that's what most of us were thinking shoppingbag but when the OP started with guns blazing 

"Total rip off, last time dealing with eBay"  it was obvious that the OP was very new to selling and as  looking

for the breakdown may confuse them  even more,   we suggested alternatives.

Let's also hope the OP has now learnt the buying basics which haven't  changed since  the site originally started .

If it looks too good to be true.....

https://community.ebay.com.au/t5/Buying/Scam/td-p/1601958