In your catfish analogy you would not pay more money for a product you could previously get for less. meaning less value. If you were given three choices at the same previous value you would not hesitate. If you were given a small. medium, and large portion to choose from at a proportionate price then you will have not lost any value. The desirability of the BNG is in the price, as well as the quality of experience.It marketing and association. Catfish was the dog of the fish world and I used to eat it because it was good and cheap, then it got rebranded as a luxury fish and bam I was't going to pay X dollars for that anymore. Same fish, different marketing.
The SP that offers the BNG at a reasonable price and offers a good experience retains her existing clients as well as every new client that tries her service. This is marketing for long term client retention.