Earlier quoted context omitted.
Right but the earlier you catch your mistake the more time you'll save in total. Generally people use 10x on cost at every subsequent step. Andy Grove famously talked about how this made the FDIV pentium bug cost Intel untold millions instead of pennies. He said when the mistakes and decisions seemed free early on, that's actually when they were the most expensive. As more commitments were made towards the design, it…
I'm a little bit confused. At first, we were talking about people using React for Hello World or similarly small and simple project, but here you're talking about making architecture decisions for huge projects?... In context of a simple project: yes, React is not the best tool for the job if you look at project requirements. But also consider the fact that the bundle size and optimization might not be that important…
This is the hidden cost associated with such decisions. If you decide to make it an SPA, you are automatically opting in for paying wages of frontend devs for the next years and not only that, you are probably opting in for them to need longer time to get browser staples back working. Things like a navigation, that could be a rather simple construct, maybe 1 or 2 days of work for rendering simple HTML templates on the server, with some nice CSS styling, can suddenly take weeks to implement and adjust. Can the most likely little need for SPA justify this extra cost?
Usually you are also not only having one frontend developer, but multiple ones to pay, since you don't want all the knowledge in one hand only.
Take a good developer salary and this can easily get into the millions over the years.