> It's not for you to judge whether the $40 is "worth" $40. It is.
What other sensible quantative way of defining value is there?
The question is do we think the position leveraged to extract that value is fair. You seem to think that price manipulation (presumably of some explicitly prohibited forms) can be unfair. So I assume you amenable to some extrinsic definition of fair play.
In your example what might be the form of advantage you exploited? It could be informational or it could be based on capital. Perhaps your informational advantage is based on diligent study of a situation or perhaps it is based on cronyism. Similarly perhaps your ability to take on the risk is based on hard work or inherited wealth. I'm not saying any of these is inherently wrong but people can and do take moral/social positions on such advantages exploited for profit. Even though that discussion might be rather intractable.
So we can define the value of the trade by the spread but that says little about whether the information/capacity asymmetries were fair. If a well functioning market is meant to approximate fairness with sufficient diversity of participants then a market anomaly like this seems like more like an exception to that rule.
I do not think it is justified to call it theft.
