Our sellers were absolutely desperate to offload some massive, horrible wardrobe on us for free. Had to tell them at least three times we didn't want it and to sort it out themselves
i.e. Take the wardrobe or you can leave it by paying me £150.
I suppose people have bundled it in as a deal, i.e. we want the curtains (£500) but don't want the wardrobe (-£150) so we'll offer to take both for £350.
Note to sellers
If you have something in your home that is a massive pain in the ass to dispose of before you leave offer it to the buyers for free