The market value is skewed by the fact that the money is tainted. To put it differently: if real estate wasn't as effective a vehicle for money laundering, prices in places like Vancouver wouldn't have skyrocketed. So while technically people paid "market value", the number is meaningless
* corrupt entity A gave me $X
And:
* corrupt entity B bought Y from me at price $Z at essentially market value.
The amount to return in the first case is obvious. The second is much less clear (since the cash was essentially fungible)