Can travel agents do anything that we can't do? We're trying to do the following:

VIE - CCS - JFK June 23/July 3

Cheapest way we can find is the following:

VIE-CCS-VIE Air France $1126 (and not fly the return)
CCS - JFK $430

We've been told by our company that they're willing to reimburse us up to the value of a VIE-CCS-VIE roundtrip, and that they're arranging payment through a travel agency (which is currently closed for the weekend).

Our question is: should we just buy the CCS-JFK ourselves now (in case flight prices go up in the next few days), or is there some chance that the travel agent can access magical flight prices that we can't?