Is trade paint any different from that aimed at us ameteurs? I bought a can of Dulux trade white gloss from a well known diy store because it was cheaper than the usual one, and having used it this morning, it appeared exactly the same. The trade colour chart has a lot more colours on it than the other one, too.
Their answer seems to imply the paint is the same spec. but thicker.
So you get more useful paint for your money (if it is the same price), in that professional can be thinned more.