Roc- basically in the short term the operating costs of the '10 were higher than the 707 or DC8; BOAC/BA were obliged to buy them due to nationalistic jingoism rather than on pur economic grounds. But in the long term it needed less maintenance, being built like a brick $hithouse, and could have worked out cheaper overall! A proposed Super Super VC10 was still-born as the 747 came in with its superior seat-mile economics.
Glad that you like our dear old jet; still one of the prettiest shapes in the sky. But VERY NOISY, I'm afraid!!