The only way to do a pricing analysis, IMHO, is to track how many quotes turn into orders while changing certain variables such as sq. ft. rate. Because you need a reasonable amount of quotes to reduce your sampling error, it has to be done over a period of time ... but let's say we're shooting for 25 or more quotes tracked at each amount of sq. ft. rate.
So, for example, you might quote 25 or more jobs at $12 per foot, then $13, $14, and $15. You would still keep whatever other variables such as difficulty, complexity, etc. that you would add in otherwise.
Then, after you have enough quotes and orders, you compile the results. For example:
Rate = 12
Quotes = 30
Orders = 27
Close % = 90
Rate = 13
Quotes = 25
Orders = 20
Close % = 80
Rate = 14
Quotes = 30
Orders = 21
Close % = 70
Rate = 15
Quotes = 32
Orders = 16
Close % = 50
As you can see in my example, the higher the rate the lower the closing percentage. In my experience, the optimum closing percentage should be around 70%. If higher, you're undercharging and leaving money on the table. If lower, then you're overcharging and losing profitable orders. Run your own tracking survey and judge for yourself. You might find that you can use $20 a sq. ft. and still hit 70%.