You could do both. Begin with a rough estimate, preferably a range (order of magnitude). If this gets greenlit, do all the things you mentioned but also just st

You could do both. Begin with a rough estimate, preferably a range (order of magnitude). If this gets greenlit, do all the things you mentioned but also just start on the project. Iterate on the estimate like you iterate on the deliverables, the estimation will get increasingly accurate as you develop. There's a bit more upfront work here that goes into the estimation, but it won't be like 25% of it is pure waste. Maybe 5 to 10%, depends on what the quality of the estimate must be. Somehow this never works in practice though, I suspect the initial guesstimate will prime the expectations of everyone involved and will be seen as a target. Clients will be disappointed if the project takes longer and frame it as such (it's late, takes longer, over budget, etc.). I suspect that in order for this to work, the initial range must be large and the adjusted estimates in the project as well as the delivery date must fall within this range. I think this is a basic function of trust: will these people do as they say or not?