All I will say is that the general thrust of this article is about right. No, they don't have a grasp of the detailed prices/values, but they have reasonably accurately identified the main 'rare' coins in circulation. The prices they quote for them are mostly off, particularly the undated 20p which is nowhere near £100 now, but was in the early days. But as has been said, it is the Daily Mail, so what do you expect, though I'm not sure the working man's beano (The Sun) or the Mirrror would have got it any better.
However, I somehow, I doubt that this guy is making quite the sort of money claimed, though there is, it seems, a healthy market for modern 'rarities' and he's just tapping into this. He's got stiff competition from other 'dealers' who also sell these coins and although the mark up is considerable it takes a hell of a lot of sales to 'make' £70k a year in sales, let alone profits. Having said this, I notice that there are many people selling Isaac Newton 50ps, yet these don't seem to be available in change yet, which suggest that people are bulk ordering them from banks and then selling them on at a profit to those who aren't willing to wait for one in change. Maybe he's one of these people. Maybe, one day, he'll branch out into predecimal and become another general coin dealer. Who knows? The only other thing is that I'd hate to have to rely on the Post Office he uses, assuming he uses the local counter. I've been at the front, with just a dozen RD or SD coins to be processed/posted and the thudding of daggers in my back from all those standing fuming in the queue is quite uncomfortable.