Mr Farish sold his business when he wished to retire as a going concern. Under his management he had a near monopoly of RTR N loco sales in the UK. Therefore, I would suggest he knew his market reasonably well. From my observations of N gauge modeller's comments at exhibitions, I would suggest he was right about a significant fraction of them.
The absence of significant volume competitors in the N gauge loco market is a notable factor; it either means there isn't a market for quality N, or that the whole UK N market is just too small to be worth creating the tooling.
I know, and that has improved OO considerably over recent years. One would hope that the trend will spread to N gauge. I'm encouraged by the appearance of Dapol, though a couple of bogie vehicles isn't a full range and we'll have to see if the initial foray results in a range of quality items.
One regularly hears comments like Jim M (who posts here) about the better quality and prices of Japanese or US outline locomotives. A number of N modellers I know have taken to modelling overseas prototypes in dispair at the quality of UK offerings.
With modern production methods it hasn't actually increased prices significantly; good OO items like the Bachmann class 08 are very cheap.
See comment above.