"No, it's less effort than that"

This is a bad metaphor. You can't make the sun come out faster by dropping features.

yeah i cannot use this analogy to tell my client to backoff.

they will say: if you guys are only watching the weather and telling me whether it will rain or not -- I dont need you guys then. I will hire someone else - who will build me a working umbrella within my budget before it starts to rain.

or some other imperfect analogy that we cannot question having done the same thing ourselves first

What you can do is release a product faster with less features and continue working on adding the missing features after the initial release.

This happens all the time in embedded systems which can be updated by the customer.