I'd be very surprised if big users of AWS or Azure pay the rates advertised on the public web sites.

Right, nobody pays /more/ than the published prices.

And prospective users can look at the published prices, and see that historically they've gone down more than they've gone up (although obviously that trend could reverse).

So people think they're safe from the risk of Amazon quadrupling their bill over night.

Of course, vendor lock-in can have other negative effects, but apparently people aren't worried about them, or at least think AWS is no worse than the alternatives.

Well, if you aren't in the US there is forex risk - Azure certainly increased their prices in the aftermath of the Brexit vote decrease of GDP against the USD.

Doing any kind of business in non-USD currency is itself not a great move.

Like most large business, AWS has a sales department and sales engineers that behave like you expect.

Rates are absolutely negotiable.

Our AWS rep is nice and cheery. He'll come into our office twice a year and bring sales engineers to hear about our upcoming projects. There's one lead developer on our team who keeps imagining systems that use half a dozen AWS services for "big data". The AWS dudes always end up talking to him the most and they definitely bait him with various pitches and, of course, feed his ego. Good thing that he's so disorganized and delayed that he never has a chance to waste company money on all that bullshit.

Having negotiated both, AWS is negotiable within a range that is much tighter than the range for enterprise sales of Cisco, EMC, etc gear. (Or AWS has better negotiators, but I've never gotten a call "Hey, Qx is about to end and I need to hit my numbers, so is there anything we can pull forward" from an AWS rep.)

They could show everyone different prices (like plane tickets)