As noted in the other reply here, there is plenty of arbitrage between the internal and external markets. I have counted at least 10 or so bots doing it, and I may have missed some (although I can't tell for sure if some of them have the same owner).
Observationally, the price on the internal and external markets is almost always much the same (as a consequence, in part, of all that arbitrage). So stabilizing on the internal market must stabilize on external markets too, as long as this relationship holds up (which it has so far, and likely always will).