Some of your most loyal customers might be quietly costing you money

Meera ran the numbers on her secondhand bookstore late one night and found something that unsettled her. Her most devoted customer, a retired teacher who visited every single week, browsed for an hour, chatted with the staff, and asked for special orders that took real effort to fulfil, had spent less in the store over the past year than a woman who dropped in twice, bought a stack of books each time, and never came back.

Meera's instinct was that loyalty should be rewarded and rare visitors ignored. Kotler and Armstrong would tell her the picture is more complicated than that, and they sort customers into four groups based on two questions: how profitable is this customer likely to be, and how loyal are they likely to stay?

Some customers are what the authors call strangers, people with little fit between what the business offers and what they need. There's no case for investing in them; the only sensible move is to try to make a fair transaction and move on. Others are butterflies, profitable for a moment but never going to settle into a lasting relationship, the way a stock market trader might chase good deals across several brokers without ever staying loyal to one. The advice for butterflies isn't to chase their loyalty. It's to enjoy the transaction while it lasts and stop spending effort on them once it's over.

Then there are true friends, both profitable and loyal, the customers worth real investment because there's a strong fit between what they need and what the business does best. And finally there are barnacles: intensely loyal, but not very profitable, often absorbing time and attention that could have gone toward true friends instead. Meera's retired teacher, with her long browsing sessions and special orders, was a barnacle. Loyal, likeable, and quietly expensive to serve.

Kotler and Armstrong don't suggest firing every unprofitable regular. Sometimes a barnacle can be made profitable by selling them more, adjusting fees, or trimming the service that costs the most. But if that doesn't work, the honest answer, uncomfortable as it sounds, is to stop investing in a relationship that will never pay for itself, no matter how warmly it's dressed up as loyalty.

Take your ten or so most familiar customers and sort them honestly into the four groups, estimating rough profitability against likely future loyalty, even when the answer is uncomfortable. Where you find a butterfly, someone profitable for a moment but never going to stay, enjoy that transaction fully and stop spending effort trying to win their loyalty. Where you find a true friend, someone both loyal and profitable, invest visibly, a personal thank-you, an early look at something new, a small extra that says you noticed them. And where you find a barnacle, someone loyal but costly, try raising a fee or trimming a service before deciding whether that relationship can ever pay for itself. Some of these conversations will be harder than they sound.