We used a complicated formula, the out door temperature divided by two, times the number of crews divided by the sq/ft of their parking lot. Works every time!
We use the sq/ft method, charge higher for areas that need more attention (entry and funnel areas) less for those that are light to moderate soil. Discounted for frequency and large sq/ft areas.
Look at what it's going to take you time wise, what do you want to target and hour? Multiply that target number times the hours it will take to complete the project and then divide that total by the sq/ft.
For example you want to make $150.00 and hour for a 2-technician crew and you have 16,000sq/ft to clean. The carpet conditions will only allow you to clean at 1000sq/ft production rate. $150.00 x 16 hours =$2400.00
$2,400.00 divided by 16,000sq/ft = .15 sq/ft
.15 is actually very high, but if each of those guys is running a machine then production will be 2K an hour so processing is down to 8-hours.
8 x $150.00 = $1,200.00
$1,200.00 divided by 16,000sq/ft is .075, you can win a lot of work at that rate.
I wouldn't suggest going that cheap until you get some experience and find out what kind of production rates you actually generate. Winning a contract where you lose money or work very hard for very little isn't a good thing for you or your company.
Price it where you make a decent return for the effort and you'll feel much better about it should you win it.