I'm not sure what you're getting at with the $500 for 500 sf foot question. I've never been one to boast high prices, and if this is an argument we're having, I didn't realize it. All I doing is trying to convey the fact that I have an account that has been a real problem for around 15 years. They, and I, have never been happy with the way the carpet has responed to cleaning. It was so bad at one point that they decided to do it in house. That lasted two years and they were calling me back.
I've tried traditional HWE, rotary HWE, GLS cleaning with all kinds of encap products (which worked really great, but not having any real extraction was a problem for me, not them) and then I tried OP cleaning. Traditional OP cleaning gave a great cleaning with no problems, but was too slow for them to be able to afford. When Clark started putting guide wheels on his machines, I had mine retrofitted to a Defender and THAT has finally been the answer.
They're happy for once, and I am making money on that account.