The dynamic you are describing captures probably the majority of all the pitches investors hear. Everyone thinks they can "recoup" within X days of spending on sales, marketing, and support. The reason to do it one city at a time is that it allows you to demonstrate two things: (a) that your model actually does work, unlike the 1000 competing pitches that claim the same thing but don't work at all, and (b) that you don't actually need their investment, which gives you leverage in your negotiation and, counterintuitively, makes you a more attractive investment.