Software developers are not negotiating fixed price contracts with their project managers every two weeks. Just how toxic such a situation would be should be obvious. Managers need to understand the context of the job and determine if they're satisfied with the productivity of their employees.
Agile is a development process not a contract pricing strategy. If anything proponents of "Agile" would be more hesitant to quote you a firm fixed price contract than "Waterfall" teams.
This is not exclusive to scrum.
> the reason given for Scrum being bad is it features estimation
This seems like a strawman and not at all what I was picking up from further up the thread.
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https://news.ycombinator.com/newsguidelines.html
> Please respond to the strongest plausible interpretation of what someone says, not a weaker one that's easier to criticize. Assume good faith.
Prices in the real world are barely linked to costs. Budget risks are bundled in markets with high variance.