I checked some past sales from Ebay.
A DS sz 10 sold in Oct for $325, it had some heel creasing like yours.
If this pair is listed as pre-owned , a similar condition sz 10 pair sold in Oct for $280
Therefore, a fair price for a DS pair is anywhere from $300 to $350 and $250 - $300 for a near deadstock pre-owned pair.
The above are Ebay prices. For a direct sale figure about $25-30 lower than the aforementioned pricing.
Good luck negotating