SCAM: Why do I have to pay return postage for seller who sent the wrong item?

[Expeditor]

I bought TWO golf bag stands. SO large items even dismantled.

I was sent what looks like a brass washer, worth about £0.01. The packaging said there were two items inside, but there was only ONE.

PayPal have suggested I PAY to return the item & then get a full refund.

I spoke with PayPal BEFORE this transaction & they told me I was fully covered buying through them.

It appears that was a lie, if I have to pay postage for what is obviously some form of scam.