Digging into the CSV records attached to CCP Quant’s October economic report, we were able to see that on the day of the ban (October 12th), total ISK supply dropped by 24.85 trillion ISK overnight. Accounting for the average upward movement of ISK over the previous month gives us a figure of around 25.77 trillion ISK that was likely part of the ban wave. This amount of ISK could currently buy you around 20,295 PLEX game time codes on the in-game market, which have a real world value of between $303,000 and $405,000 US depending on the price paid per unit.
Keep in mind that these figures account for only the liquid ISK in the banned players’ accounts. The value of any assets frozen on those accounts could bring the total even higher, but the frozen assets can’t be verified at this point. The bans came after intensive investigation of the accused players for real money trading offences, and happened on the same day that CCP announced that all third-party EVE gambling websites would have to shut down.