There are countless methods, here's mine. Design the system (i design mine down to the last fitting). Create a spreadsheet (excel) that has a list of the fittings (heads, pipe,fittings,point of connection, nozzles, etc). My spreadsheet has a cell that I key in my cost of labor (ie. burden rate). Each fitting also has a factor as to how many can reasonably be installed in one hour (ie. 6 rotor heads per hour). Each fitting also has a profit margin I want to obtain on that fitting (ie. heads get 40%, pipe 50%, etc.) So for each fitting, I calculate installed cost (=material cost + [labor cost/# installed perhour]), calculate selling price (installed cost/(1-margin%)), multiply by quantity, then add up the list. Don't forget to make provisions for special things like hand digging,washing under walks, tree roots, equipment rental, etc. Also make sure that you have your business overhead figured (say o'head is $1000/week, job will take 2 days, need at least $400 profit just to contribute to o'head). And make sure that you pay yourself also. (ie. another way to price would be this... I want to make $50,000 year personal income, business takes $50,000 in overhead and retainer for growth/repairs. if there are 200 working days, this means I need $250/day, business needs $250/day. If job takes 2 days, then profit needs to be at least $1,000 to meet the goal. Calculate costs, estimate times, add $1000 in this case.) From what I have found, for me both methods work out about the same price.
Like 3horn said, there's so many ways to figure sprinkler cost.
I only work with fixed spray sprinklers because of the small areas I do. I figure $45 per head plus anything like walkways, driveways ($6.50 per foot) big roots ECT... Depends on what you want to make an hour doing sprinklers. Know how much everything cost first. Fittings, pipe, timers, valves.