I agree with Groovy Jon completely. His experience mirrors my experience, cleaning commercial carpet for many years.
But here's a strategy I learned that works. Offer a vacuuming discount....
THIS WON'T WORK:
It's hard to upcharge for vacuuming. Tough to sell!!!
People will scream if you say, it's $700 to clean the carpet, but if we have to vacuum, it will cost $1,000.
THIS DOES WORK:
People LOVE to get a discount. Explain how critical good vacuuming is prior to cleaning.
Then say: "You guys already have a vacuuming program, right? Well, here's what we can do.
The carpet needs to be vacuumed REALLY WELL, before we clean it. But they'll really need to do a thorough vacuuming.
The price for carpet cleaning is $1,000, but if you can have your janitor do a super job vacuuming, we can discount it to $700."
You've attached a dollar value to the vacuuming, and they own it. They'll be thrilled to get their person to vacuum in order to save money. Emphasize the need to do a really thorough vacuuming. And understand that their vacuuming still may be less than perfect. But normally it's a good start. Sure, we may still do some additional vacuuming in the high traffic areas. But we're not responsible for the paper clip in the corner. And it's generally a big improvement over a building that wasn't pre-vacuumed.
Works like a charm! Try it.