You pay for a car based on (1) the cost to build the car, including any added options that upped the price and (2) whatever profit the dealer can make.
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In the case of Tesla, they are not charging $10,000 more for the same model and battery because they built a better battery. They are charging $10,000 less because they took that same battery and "hid" its full potential via software manipulation that reduced its performance.
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Think of it this way. You and a friend buy the exact same car that has the exact same features in every way, shape, and form. Same engine. Same battery. Same everything. Except in one area: Software programming. And you paid $10,000 more, not because you got a bigger and better battery, but because Tesla took the extra steps to manipulate his battery to operate less efficiently. 
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You might feel justified to spend $10,000 if you, in fact, got a bigger and better battery than he did. But you didn't. He just got different programming for $10,000 less.