According to the MLS number in the link you provided, you are referencing Penthouse Unit C. This particular was last listed on the MLS in 2008 for $3,350,000. If you are serious about buying this unit I can try to contact the unit owner and see if they are willing to sell. Otherwise, this particular unit is not being advertised for sale on the MLS.
However, there are several units similar to that one for sale that I'd be happy to show you.
401 N Wabash - 3br 4.1ba at $3.5M includes two parking spaces
Several Single Family Homes in the same area 5000-11000 square feet at $3.3M-$4M
30 W Oak 4br 4.1ba at $3.35M
25 E Superior 6000 square foot penthouse, raw space for $3.3M, developer willing to finish and let you customize for additional cost.
50 E Chestnut - several large units from $3M-$3.7M
If you'd like to learn more about these units or other ones like it, let me know.
773 677 5340