Even if there is evidence to prove that it was the spelling mistake which led to the lower sales for this company, it is entirely reckless to make a statistical analysis of the entire UK on-line economy based on just one website.
How does Duncombe know that the sales were permanently lost to the UK economy? Drawing statistical conclusions from a miniscule sample size is just as heinous a crime as poor spelling.
Hat-tip to @SueWalder for the link to the You Tube clip below on the the impotence of proofreading.