This whole thing is a scam, really. Here's a company making billions in profit at the expense of thousands and thousands of retail jobs, and it's looking for corporate handouts and tax breaks. Like Walmart, Amazon is likely contributing to the decline of city centres all over.
It's pretty demeaning that Amazon is dangling the carrot expecting everyone to jump, when it really should conduct its own research and analysis for the best location. If I were looking for a new house I have to search on my own or hire a real estate agent. Cities are going to spend a lot of time and money pitching and won't get paid for the effort if they don't get it. it smacks of
work on spec, and reflects on how they perceive labour.
In the end, some city is going to get fleeced to provide concessions, and Amazon is going to suck most of the money because it thinks it's entitled to the economic windfall it produces instead of owing it to the place that gives it a home.
Personally, I think they should just stick to Seattle and swallow all the costs since they are part of the reason that city has become so expensive. If they build it into their pricing maybe the rest of the global retail business environment has some chance of remaining competitive.