"What ROAS can you get us?"
Unknown before seeing the account, and meaningless without your margin. Anyone who answers this is telling you what closes the deal.
"How much should we spend?"
Depends on your price point, CPCs and conversion rate. We will give you a real number after the teardown, worked backwards from your break-even.
"Will this work?"
Depends on whether demand exists and whether your margin can pay for it. Both are answerable — in about an hour of looking, not in a sales call.
We would rather be the agency that said "I do not know yet" than the one that guessed and was wrong in month three.