I've always heard for the Thursday game tickets they are easy to get (lower seeds playing) from scalpers. For Friday (2nd round) when it's in Indy you can expect to pay $80 to $150 depending on where you want to sit and who is playing. The toughest ticket is for the semifinal games on Saturday. Championship Game tickets on Sunday are actually priced a little lower than semis because the other ten teams have gone home.
All of this depends on which "local" teams like IU, Purdue, Illinois are still in as they have fan bases within a couple of hours of Indy. Also, scalping is legal in Indiana as long as you are not on the property of the venue … across the street or in the local bars is fine.