The 1000 Fans Theory
A theory coined by Kevin Kelly holding that an artist or other content creator needs just 1000 enthusiastic customers to forge a career. The simple math employed in this widely cited and influential article reckons that the enthusiastic fan will pay $100/yr, yielding net revenue of $100,000/yr for the creator.
Whether the specific math is right, or whether it be 100 fans or 2,000 fans, is not the point. The point is to focus on cultivating small, targeted, niche audiences.
This theory is mis-applied to consultants and entrepreneurs; they have customers, not fans. Thus, they may need far more or far fewer than 1000. For example, a healthy consulting services business has between 8 and 12 customers a year, for a total of perhaps 100 over a business-lifetime.