Ask the "fast track" subscribers and the hundreds of other cleaners who just blindly copy that tag line!
The way this was incorporated into the fast track system, meant that they were aiming at big-paying clients... the kind with big rooms of not usually very dirty carpets. All about clean & sell protector and a maintenance plan. Not the sort of customers to usually be worried about quibbling.
Giving guarantees is proven to increase response rates to ads and conversion rates of quotes.
The statement you've quoted is actually meaningless - I'd like to see a court case based on it! Obviously there are T&C's provided with written quotes, it is carefully worded and thought out.
As with a lot of things, we know it's BS but it sounds good to the prospective enquirer so that's how it does its job, by making them pick up the phone.
The statement is really a candid way of saying "we are not cowboys and we charge a fair bit". If you were a council house dole scrounger looking for the cheapest price, would you ring an ad that said "Charlie's carpet kleenerz, cheepist in town" or one like the one you've mentioned? It's a filter, it suggests you are not going to get a cheap quote from them. Quite clever really!
My YP ad is very blunt to discourage price shoppers, it says in big bold letters at the top "For cheap quotes please enquire elsewhere"