You know that all customers are not equal, some are more profitable than others

It consumes time, resources and effort for each marketing campaign and sale, what is the return on less profitable customers?

A further consideration is the cost of processing and fulfilling orders for marginal customers

While you probably don't want to say no, or drive away marginal customers, you can avoid targeting them for active sales and marketing

Most companies have very good data about customer revenue by product, do you have profitability by customer/product?

Develop a profitability, rather than a revenue profile, and target customers that fit the profile

Is it possible to reduce the handling, or automate sales & fulfillment for marginal customers? Do you have data on sales, order taking, and order fulfillment transactional costs?

Do you have market research detailing who to market to, do your campaigns focus on them, are your sales efforts also focused?