I don't think you understand my position. I don't have in mind the extraordinary cases of misjudgment, deceit, etc. I'm talking about the every day transactions. If I work for 8 hours and get paid x amount, comparing the x amount to what that roughly correlates in purchasing power, I've esteemed that my labor and the x amount are roughly equal in value, or otherwise, I've esteemed that my labor is worth less.
Well, presupposing a vacuum, and presupposing that I were a perfect rational calculator, and the transaction were conceived solely in itself in isolation, then indeed, my estimation would be a solid one.
But that's not what happens, is it? The transaction occurs under competitive market conditions according to agents who are performing the transaction with a capitalist mindset. As a matter of fact, it's clearly evident that my estimation, under these conditions, is bound to be wrong at some point. Because of any extraordinary flaw in my judgment? No. Something completely commonplace in a capitalist economy: price fluxuation.
A boss will, on occassion, give me a raise, and that raise may or may not be related to inflation. Well...was my work any more or less valuable the moment before I got the raise than after, considered in itself? No, my work remains the same. Did I make an error of judgment in selling my labor at too low a price when it was worth more? Did the employer make an error of judgment in paying me more when my labor was worth less?
Another example: The moment after the Playstation 3 came out, it cost x. A year later, it cost x-y, where y is the difference between its initial cost and its cost a year later. Did the value of the Playstation 3, considered in itself, change? No, the Playstation 3 remained the same in both cases, presumably. Yes, yes, the Playstation 3 underwent certain changes, but I don't think that these changes had anything to do with the price.
Well...no...neither. Market prices don't reflect actual value. They only reflect market conditions. When I make an estimation of value, I'm not estimating actual value to me. I'm merely estimating the market conditions. I'll purchase the milk for $3.50 a gallon, not because it's worth so much of my work or because it cost that much to produce it, but because I can't find it any cheaper. Again, the milk producers sell the milk for $3.50 a gallon, not because they esteem that the milk is worth so much of my labor or because it cost them that much to make it, but because they esteemed that $3.50 is the most for which they would be able to sell it.
As a matter of fact, I think that deceit/exploitation/etc. more or less are built into the capitalist system, and that's because capitalism is based on one big lie: that a human being (or his labor) has a price tag.