Hi , mate , i asked the same question a couple of months on here . The answer of the pro c. cleaners seems to be that it is not pro enough , i have a G4 kirby and for vaccuming your carpets , nothing can touch them , they really are the best , now unless Kirby have up-graded the carpet cleaner over the years ( mine is about 15 years old ) i wouldnt go to a posh house and try and clean the carpets with it ( in hindsight ) . they are fine for maintenance cleaning though .
ps..............if Kirby are like they were when i did it some years ago ( 15 ) your mate as his work cut out to sell them (unless he is a fantastic salesman ) . I worked all over Manchester and try selling a £1300 carpet / vac cleaner to someone who cant afford wallpaper on their walls . You have to stay there for 2-hours demo and trying to sell then your gaffer will ring them trying to hard sell the machine . I sold about 14 in six weeks before my conscience got the better of me and i quit , but it did teach me a few things about how to hard sell , which i have used over the years
hope this answers your question mate