Some startups may be amenable to slow bootstrap, but the ones that have this very high wage cost tend not to be those types startups. I love these kinds of hardcore tech startups and believe they are extraordinarily valuable, it is the kind of company I would start, but I am also very realistic about the economics of building a team that can execute within those constraints.
Short version: you can either generate project revenue or product revenue. You build a fundamentally different company to do either, so if you spend a significant portion of your time in project mode, the time you spend in product mode is usually moot. Consulting companies are project companies, through and through. The widely regarded truism that project companies cannot be transformed into product companies exists for a reason.
I'd love for this to not be the case but I've lived it so many times that I thoroughly understand the reality of it.
A lot of the best SaaS companies have actually come from consulting businesses that were productized. C.f.: https://startupsocials.wistia.com/medias/e6ttk04b9e?fbclid=I...
I think this strategy has a bad reputation because it usually fails, but what people forget is that startups usually fail anyway.