Re: Availability Zones
Those that don't have the budget presumably are spending it on features? That's not about cost that's about where one believes the revenue is ie features. However, if you're down, your features don't get used. A similar argument can be made for time expended in building HA: You can expend engineering effort once or support and admin effort every time you're down.
Ultimately, this is about your users. Do you care enough about them to put their fate and yours in another's hands or do you choose to use the available facilities (and if you used a DR style arrangement you could save much of the infrastructure cost until time of need, magic of elasticity) to protect everyone?
No doubt, for a fledgling company the choice has to be features but it should be a knowing choice. Amazon make it clear what needs doing for HA, choosing not to do it is on the respective business owner. For those with a decent paying user base the balance is somewhat different, all about how much you value your reputation. Blaming Amazon for your downfall will be limited consolation for your users. If you fall victim often enough you'll be paying the cost in lost revenue through inaction and support interactions. Alternatively you can pay the cost of moving clouds or developing your HA options.