I charge for the mulch plus one one hour of labor for each yard. Example: mulch =$20.00 + $35.00 labor = $55.00 per yard. You could always charge more for the mulch and make a profit off of that too but I find that I can actually lay at least 2 yds an hour in beds that have established plants in them.
If your having the mulch delivered by someone else,figure out how much you want to make per hour wheelbarrowing and laying your mulch.Then factor in how much your business needs to make an hour to turn a respectable profit.
If you're going to pick up the mulch and install it,figure in your hourly pay,your company's hourly pay(with gas,equipment replacement costs,maintenance costs,insurance,taxes,etc.,,) and charge enough to make plenty of profit for yourself and the business.
You ,as a business owner/operator deserve to be paid well for your work.I can't tell you how much to charge,because I don't know what kind of
money you need to make a profit.Just be sure it's worth your time.After examining my costs versus profits this weekend,I've just raised my prices.