There have been business-class-only airlines, and most (all?) have failed.

Depends what you mean by high-end clients. There are over 100 million households in the USA, so even a product marketed to The One Percent has over a million potential customers. Many "private" banks issue payment cards only to their clients, but we cannot judge the profitability of the card products because they are bundled with wealth management services. Also, these cards are often administered by another card issuer, such as Elan Financial Services, because it isn't cost effective to do this in house with a small customer base.