Quote from StarDust9182:
SLE: You are right. I used listed when I shouldn't have. I don't trade such animals, I trade options and am always suspicious of their pricing as well. I treat the options market like I knew for certain everyone around the poker table is double-dealing and taking a cut when I look away or go to the washrooml.
Another example was libor fixing. How is that even possible? If that can be fixed, then anything can be. I remember that everytime I sit down at the table.
The same argument about mis-pricing not being obvious at the time applies to every instrument. Just because you "know" (or suspect) that something is mis-priced doesn't mean it will revert in time, nor that you know the direction of the error or the amount. Usually an "arb" trade can be fashioned as you say. In my book, an arb will not lose and if I am not certain I pass on the trade.
Mark to market is not really relevant since the point of an arb is that at some date simply by holding, the true price MUST appear. (BTW, I know of one case where a true convertible arb actually lost money without trading! Nothing is impossible in the markets.)
Volatility may have no physical meaning at all though. In electical engineering we do a lot with the square root of minus one. We are taught it is simply a convention to make the math of the model work and that there is no real world equivalent. It is a communication term. Implied volatility is similar. It makes the math work and some people start believing in the model or terms more than the real world. However, no model of the universe can be perfect or it would be a one-to-one replacement of that universe. Simplification can throw out important data as "assume".
In summary, different semantics aside, we are indicating similar thoughts.