This kind of thing happens a fair bit in this industry.
I know of a few sign-makers that have gradually got bigger over time, then bought a router so they can do large jobs more cost effectively than getting them supplied by a 'trade-only supplier'. They can then supply the trade as well, and this is one thing that is mentioned by the people selling the routers, as a selling point.
So what they then do is set up another business, so that the two companies are different and then they say we (business 2) only supply the trade.
I don't know whether the company that you talk of, have gone the other way and gone from supplying the trade to supplying the public.
It is frustrating, but I can understand why they do it, and if I was to expand my sign-making business, one option would be to start supplying the trade, as I would obviously have some of the expertise required.
Fair? - Unfortunately life isn't.
Life is pretty tough for the small man.