I think the issue is not that the exchanges charge too much, or that the prices aren't different between the exchanges (they are, sometimes vastly so from what I've seen). The problem as I would see it, is that you can't extract your funds in USD or another fiat currency quickly enough... so you might be waiting 48 hours and by that time the exchanges likely will have leveled off the difference.

Maybe someone else has some input as well.

You sound suitability convinced? Why inform other of the potential millions to be made. Go forth and earn said millions.

It's hard to get USD and such in and out of certain exchanges. Exchanges with easy deposits and difficult withdrawals will have higher prices usually. Moving the bitcoins isn't ever a big deal.