Who can explain the mind of the simple?
It could be a typo on the part of the seller, simple enough.
It's more likely the work of communist cretins who creep on their belly and lie in wait to ambush the naive. Unbending fellows who drink others' tears and sup on inequity. Their kind is far too many and inclined towards malice for selfish gain.
In my experience, accidental or grossly "unfair" trades always get reversed by righteous admins...so they wait in vain.