The writer of this note learned the hard way. In 1975 he had a business selling body building equipment and learned that The Sun produced responses at about one-third of the cost of the other media he was using. He therefore took the ill-judged decision to put all his money into The Sun. Conversion rates in the Sun were so abysmal that he made no money whatsoever. This was compounded by a shift in currency rates, which made the product much more expensive to buy, and eventually these two factors combined led to the firm having to close down.
Diamonds are nothing more than chunks of coal that stuck to their jobs.