Wow, I knew he was old, but had no idea he wasn't well. Aftermarket movement of BRK.A/BRK.B seems to be muted, so I guess right now investors aren't too worried about the future of Berkshire.
Most of the trades in that stock have been routed through dark pools (they don't hit lit exchanges), so even if there are (huge) trades you wouldn't necessarily see the price move.
So you're saying there is an arbitrage opportunity and you can literally make free money? Because that doesen't make much sense..
You might not see all the trades immediately, but they are still reflected in the price with minimal delay.