Sedo, Afternic, Ebay, etc are not auction houses, brokers, etc ... when a deal goes bad, they go into hiding with their answer being work it out yourself - we can't be bothered; it's not our problem.
On the bright side, one can take advantage of that lack of regard, and many do; most obvious way is bypassing Sedo, Afternic, Ebay, etc when it comes to doing the actual deal...
And because Sedo, Afternic, Ebay, etc aren't licensed, they won't do anything because otherwise they run the risk of getting into the middle of a murky legal battle...
Basically, except in rare instances in which one of above mentioned services has truly added value to a transaction (yes, occasionally they really do), buyers who overbid due to shills and the sellers who paid the 10% or whatever commission are chumps - harsh, but sadly is the reality.
Ron