£10 is a ridiculous price for a £20 item.
That's usually for a £40+ item as once you factor in postage and fees, it's just not worth it.
I.buy and sell lots on vinted.
Ie. New price £160
I price it at £39.99 probably get £30-35.
New price £20
I price it at £7.99 and probably accept £5 as even with that they are paying £8.50-9.
If you are realistic on vinted then you sell.
Just remember that once you have bought the item, stored the item for however long, the new/original price basically means nothing.
If you don't want to give it away for free, whatever you get is whatever someone offers you for it.
And the cost are sunk anyway, you already spent the money anyway.