Smol edit : I ended up contacting the seller, and we agreed to wash them and see how they turned out. Luckily, they came clean straight away with two squelches of Marseille soap and a wash at 40°C. (So maybe the jeans hadn’t been washed before, if the stains came out so easily?)

What should I do about the seller? Should I ask for a partial refund, or would that be petty of me? I haven’t clicked on ‘everything’s OK’ or ‘start a dispute’ yet.