Economists HAVE addressed this, but not directly, AFAIK. It takes two steps to explain what little I know about it.
I. Of the several different market structures, the best, from a consumer’s point of view, is perfect competition between businesses. This involves a whole set of market characteristics, but the relevant ones here are that the businesses are indistinguishable to the customer - products are of identical perceived quality, same price (which in perfect competition is forced to be as low as possible while still supporting the business), and are equally accessible to the buyer.
II. Curiously, you can turn around the market relationships and similar principles hold. That is, from a business’ point of view, the ideal situation is a perfect market in customers. Where above businesses were thought of as competing for customers, here customers are thoguht of as competing for the attention of businesses. The new situation is symmetric with the old: economics most favor profits when the clientelle is undistinguishable, and analogous relationships to the above hold for this reverse relationship. The buyers should behave the same ways, be willing to pay the same prices under the same conditions, and be equally accessible. Economists have done a reasonable amount of work on this sort of thing.
The reason for these relationships is best understood in terms of bargaining power. If you, as a consumer, can go elsewhere for what you want to buy, you have bargaining power, which can be used to get a better price; or, in the case of a business, you have bargaining power and can charge a higher price if you can always go to different customers. That’s a bit simplistic, obviously, but it captures the general concept.
The worst case for the consumer, best for business (at least from a price point of view) is when a monopolistic business sells to a mass of interchangeable customers.
The best case for the consumer, worst for business, is if they are the only buyer (like, say, the government often is for defense contractors) and they are buying from a large pool of identical companies (perfect competition - NOT the case for defense contractors, which is why they’re still in business).
This is a fascinating subject, but I’m no economist, so I’ll let you pursue it further for yourself if you’re interested.
Bottom line: there were (and still are) certainly financial costs to American businesses that stem from the heterogeneity of consumers. The more heterogeneous the customers, the more true this is, so the Jim Crow laws created a less profitable situation for businesses than equality would have. Since equality was not the situation they were faced with, businesses adapted and kept blacks and whites separate, simply bearing the costs.
[You realize I’m speaking not as if businesses make these decisions consciously, but in the faith that they respond to market forces. I doubt white business owners realized, individually, the costs associated with Jim Crow, but if the social attitudes had been less restrictive I’m sure that over time the less segregated businesses would have had competitive advantage over the more segregated ones.]