Upon reading your posting, I looked up the ingredient listing of Small World Complete Rabbit Feed. It is surprisingly not a bad feed at all!!! Of course, I would still feed my rabbits hay if I were you. The pellets are alfalfa based with a high crude protein amount at 16%. Adult rabbits should only need 12% crude protein. I would regulate their pellet intake at the 6 month-old mark. They really should not be consuming too many pellets after they reach 6 months old because pellets are to ensure your rabbits get all the nutrients they need that they would otherwise get in the wild (domestic bunny in the wild haha). Too many pellets is pretty much like vitamin OD in people.
Adult rabbits should be eating timothy-based pellets but it is not a big issue if your rabbits are eating a lot of hay. Some pellets taste so good that rabbits neglect their hay. Only then should you be concerned.
I have been researching online and writing adamantly about rabbit feeds lately. Perhaps you may be interested in my other postings as well regarding rabbit feeds. I found some things to be horrific, such as American Pet Diner's rabbit feed which contains sodium lignosulfonate. It was the 8th ingredient in a long list of ingredients and may cause lesions in the colon and in extreme cases, death. I am waiting for their response concerning that.
Another ingredient is cane molasses/molasses. The purpose is for binding (less powder) which reduces dust (less waste & respiratory issues) but it is also for taste. Rabbits love sweets. However, it will make house rabbits fat and rot their teeth over time. Unfortunately, a LOT of rabbit feeds contain molasses, including Manna Pro and Purina. Sweets, as you may have read already, are not good for the gut.
I now feed my rabbits Oxbow's Organic Bene Terra Rabbit Feed. It is quite expensive but it has safe binders and is timothy-based. It is the ideal feed for a rabbit, in my opinion. However, your bunnies eat an incredible amount. Mine are tiny little things. You mentioned the price of industrial rabbit feed being lower than the commercial brand, well it usually is. I guess marketing really brings up their costs?
To sum it all up:
Small World Rabbit Feed is a surprisingly decent rabbit feed that is worth buying for your rabbits.
However, although hay is "not required," it is highly recommended by ALL experts for the health of your rabbit. A rabbit will survive whether it gets hay or not if they are eating pellets. However, the age it lives to is questionable. Quite the misleading statement, don't you think? *sigh*