This is the exact same experience I had earlier this year while booking 12 tickets for New York to Beijing. Group sales offered me a rate of $1011/person, and I told the agent that I was looking at a price of $860 online. She said that there were less than 10 tickets in the fare bucket I viewed, and she had to place the entire group in one fare class at the higher rate. Frustrated after going round and round with her and a supervisor, I canceled the group and booked them individually. 9 tickets at $860, 3 tickets at $895 - total out of pocket savings of over $1700.

It really makes no sense to me why I had to "game" the system to get open market fares. Not even a discount for group volume, just getting the fares that any transient customer can pull up at UA.com