Quality Revenue

Predictability: I think more than just year to year revenue is a key here. That you need recurring monthly income/services and you need to be aware of the churn rate of your average customer. That way you can work on getting more customers and keeping them longer. Business in it's simplest form is the study of results and how to scale those results.

Profitability: Profits matter but in the end margins only matter when compared to similar businesses. The economics of scale can make even the slimmest of margins into millions. What the proper margin for any business is here I can't really say. But the owners and managers of these business should know.

As for Amazon they ride very very thin margins and deal in loss leaders. This is not something that the average consultant can or should do. But in retail it is the key to domination. But Amazon like many "internet" businesses has a problem with profit. Many of these internet businesses act like profit is a secondary concern and only the biggest such as Amazon get to the point where the economics of scale allow them to profit but even then the profit is much lower than it should be. The lesson here especially for consultants is that Profit is not a bad word and in consulting you should be profitable from customer #1. If you have multiple clients and you are not profitable or not profitable enough your model is not sustainable long term. Period, end of story.

Diversity: For most businesses this makes sense but for some the greater risk involved with one or more large clients is worth it when it allows them to employ a very small team, perhaps only themselves. And for many consultants starting out a few small clients is likely better than servicing many. Scaling is where you will get them all to a lower percentage to help eliminate the risk to revenue that is inherent in a few large clients.

IMO all businesses should scale but some people really want to be just a small team or one man show. And for them the risk can be best mitigated via customer service. They become so important to these few companies that they are indispensable. And many many consultants set themselves up like this. Yes they are really creating more of a job vs a business but that is what they want and they have figured out how to do it well and how to make a lot of money at it.