The family office managing the money of Alibaba execs Joe Tsai and Jack Ma recently purchased a condo at 220 Central Park South for around $190 million — a condo that last sold for $93 million. This extraordinary, almost 100 percent return shows how its becoming difficult to use comps as a way to compare luxury home sales across certain markets in the U.S.

You'll hear from Hiten Samtani, The Real Deal's associate publisher, and Jonathan Miller, who runs an appraisal firm called Miller Samuel.