Price transparency can harm prices. Competitors can use it as a mechanism to signal appropriate prices to each other in order to reduce pressure to reduce prices. It's highly industry/context specific but transparent pricing does not always mean better pricing. In fact, in limited contexts, price fixing can lead to better pricing.

I think Westinghouse was the big FTC price-transparency-can-be-bad case.

That's orthogonal to the post's issue, though: he paid exactly the price he was quoted for services rendered; that he didn't understand the services he was consuming isn't really Amazon's problem but it's great they jumped in to help a $0 account (which, of course, was self-serving)...