Wait wait wait hold on.
How do we know you're not just going to take everyone's bitcoins and sell them at a low price to yourself or something? I'm surprised everyone's so eager to join this group.
To directly answer your question: you have no way of knowing. However, since I only earn a profit when you earn a profit, my interests are aligned with your interests.
A bigger picture is front-running and market-moving, as a function of volume.
This consortium is practically an inevitable phenomenon in the Bitcoin trade biz.
The need, always, is for healthy competition.
Otherwise it's just a game between market-moving and suckers.