Ruinous is not "the quality of having led to the ruin of a specific entity". Rather, it is defined as follows:

disastrous or destructive: a ruinous effect on the environment. • costing far more than can be afforded: the cost of their ransom might be ruinous.

I think it's pretty obvious what's being destroyed: the ability of local jurisdiction to collect tax revenue from large cooperations. Without this little beauty pageant of ugly capitalism, Amazon would still hire the same number of new employees, possibly even in the same locations. Only difference is that a billion $ could be invested in public goods, instead of going Amazon shareholders'.

The cities who bid obviously did a calculation and decided that it was net worth it... otherwise why on earth do you think they did it?

And it's not a zero-sum game. Perhaps a better proposition from a city makes a more productive Amazon? We're talking about efficient transport and things here, after all.

Your approach is let everyone make things equally as bad and let Amazon pick any of the worst. Amazon's approach is 'what can cities do to help us maximise both our success and yours?'

I think it's positive and constructive.

It's death by a thousand cuts. If Amazon really needed to expand their HQ and add 50,000 new jobs, they would do so regardless of any tax incentives. By pitting cities against one another, Amazon privatizes some of the gain that would have otherwise been public.

Repeat a few hundred times in cities around the country and huge sums are being handed over to corporations needlessly.