I know Rob, it was a bit tongue in cheek. They have no control over 2nd hand coin prices, especially ones from circulation, but I do sometimes feel that the odd error/anomaly that seems to occur certainly doesn't do them any harm. I think it's possible that a lot of new customers may have ended up buying RM products after the whole fiasco with the mule 2008 20p and the later problem coins that came to light after see them selling for enormous prices (enormous asking prices usually, selling prices are of course quite different!). All these things get reported in the media and talked about a lot and I know lots of people that seem to think buying new coin products new is a good investment. There were companies (that like to pretend to be a 'mint' or in some way associated with a mint) selling mule circulation 20p's in special boxes with certificates that they printed themselves... some even offered the mule 20p as a gold plated ltd edition and I think a lot of people can't really tell the difference between the RM and other sellers of hyped up new coins (from a business practice point of view there are actually very few differences!)
Many even speculate on new coin products hoping for a low mintage when the mintage figures are released a couple of years later, or hoping for an error or something out of the ordinary. People have become so obsessed with potential RM errors that some even make a big fuss about spelling mistakes on the accompanying packaging/literature. Many don't really understand the nature of the errors/anomalies. The whole thing with the IRB no denomination Battle of Britain 50p for example.... it's common because they made thousands of sets and they'll always be available, but it's been talked about a lot because of the missing denomination and I bet even the suggestion that it was some kind of oversight caused more people to buy them than perhaps would have done so normally.