Why is this so expensive?

usually as a placeholder without taking the item down, might have some offer applied to it. Don't know the specifics in this case.

place holder. i have seen a toilet plunger for £999.99 before on ebay, and it is a place holder for when they have stock back in.

It has a kilo of coke in each pocket

Presumably they've put the decimal point in the wrong place. You could contact them via eBay and ask/tell them?

Cos someone pressed the wrong buttons on the keyboard

My first reaction was it was marked that high as a place holder (seems standard practice for large volume sellers to keep their place), however after following the link I'm guessing it has been a miss click - they probably meant to start at £30.
As others have suggested - why not ask the seller directly?

To compensate for the low postage cost?

Grab a bargain no returns

It must be a mistake, as it's second hand / used, coat from Zara.

I have seen people over pay for things on eBay all the time. They either seem to be unaware how much a new one is elsewhere or just get caught up in the bidding and end up over paying.