I do not dispute any of the last two points, but fundamentally potential over-valuation and under-valuation of players of at any tier exists, and it is by exploiting this misalignment that fantasy managers achieve success. In my view it is possible to say that Markakis is valued where he should be and that Jones, although inferior and more risky, is still not valued as highly. Therefore, there a value opportunity to exploit, as there is between any 2 players where one believes that market values are high or low. We all identify these disparities all the time and it is by being more right than wrong that success is achieved.
So I still don't get what the original poster said that is so absurd. He could be castigated for over-valuing Jones if someone disagrees, but there seems to be no logical disconnect in saying that based on is opinion, Jones is undervalued and that Jones + the SP that Markakis would fetch in a trade is more valuable than Markakis + whoever gets waived. My contribution was merely that the ratioanle for these types of deals is even more convincing in a deep league, when the last guy on the roster carries far less value than in, say, a 10 team league.