Hi Bob,
After long years of thinking like you, in the above sentence, I came to the conclusion that there is a "catch" in the "cost/performance" equation.
The "catch" is that it doesn't take into account the budget potential of the buyer.
In other words, if you have $5000 ready to be spent in a lens, your "cost/performance" evaluation may be radically different from the guy who has $500.
Who is right ?
No one.
Cheers,
Ruben