I'm interested in knowing how Seatgeek can calculate the value of tickets when they don't incorporate the prices of Ticketmaster, the primary seller of most tickets in the U.S.?

It seems that Seatgeek only takes into account the prices of SOME resellers. For instance, they also don't have prices from Stubhub.

We are developing a web site (http://www.seatmyass.com) which will have prices from both Ticketmaster and the major ticket resellers (Seatgeek, Stubhub, and Vividseats).