Too much is of course a subjective term. The problem with ebooks is that once the book is written they lack scarcity which makes them fairly different from most consumer products. A market clearing price is sort of weird in this instance since we know that the supply can expand to meet infinite consumer demand.

If the parent poster is correct then we'll see a price correction towards a lower price. We'll also see a more active black market appear as has happened in the world of music if the price doesn't drop.

The 9.99 price is likely low enough to discourage most market participants from piracy but if it goes much higher then who knows. To suggest that the state of the market as we see it now is the optimal one isn't correct since the free market should always be fluctuating as things change in the world.

That said if the price was really too high then no one would buy ebooks and everyone would have fixed that by now or decided to abandon the idea for the time being.