You shouldn't take free downloads as a measure of anything. People will download free shit religiously and you'll never see a single sale for it. It's the sucker game as far as Amazon is concerned. No offence intended.
There is already the 10% sample anyway with ebooks, so making your work free is just inviting the grave robbers early. Similarly with pricing, in my opinion. A few years ago, a guy named John Locke (not to be confused with the empiricist) was heralded as having sold a million units. Which is genuinely great, until you look at how.
His price was / is 1 dollar for every single novel, meaning that he uses the 30% royalty (1 to 2.99 USD, 3 to 9.99 is 70%), so that before taxes he made a total of 300k. 200k after taxes (which is 30% minimum) over a multi-year period of time. That sounds like a lot, sure.
But then there is "the very rich indy author" by the name of Amanda Hocking, who has also reached the million+ territory around the same time. She sold her novels at 2.99 to 4.99, meaning she gained 70% right off the bat. She made at least 2 million before taxes (less than 1.4M after obviously) versus Locke's "impressive" 200k. So she made five times what he did, with the same amount of sales. And that was just first the million. I imagine she has sold a similar amount, if not more, since then.
That's why the erotica 'spammers' (my opinion obviously) price at 2.99. Because less than that means: "I want to be fucking robbed". Putting your shit up for free (one book in a series) is used by people who have many serials running. Even Hugh Howey has a free version of the first Wool story, because people will buy more of what they know, but then you're going to need to have a lot more so you can afford that loss.
If you're not a serial writer, it's probably best not to play this game.
Which is of course why Amazon want ebooks to become cheaper. So they can use the numbers without having to pay a lot more.
Consider: 1M times 0.7 is 700k, 1M times 0.3X3 is 900k. They don't make real profit on the 2.99 to 9.99 range compared to the other ranges. Their profit range is either less than 2.99 or above 9.99 (which is also 30% for self publication).
In a per-unit profit analysis, they would immediately see their margin (versus paying people that is) is a lot bigger for the 1 dollar suckers.
Insert Robocop line.
edit: I feel like I've made this post before. It also should be noted that I was only referring to how this system works, not to an individual.