Pricing metrics are not as easy as they sound. Like most problems we want a simple solution. For this question there's really not. When folks ask us this question the response is the same. I can't really tell you how to price, I don't know your area. We've got to a position where we know how to quote most jobs in our community just by looking at them.
If you want a model, this is about as good as it gets: $10-$15 sqft w/housewash, $20-$25 sqft w/roof cleaning, $.50-$1.50 sqyd w/flat work. You can adjust as needed for your neck of the woods, some places garner more than others. This model isn't perfect however, it has it's disadvantages. For example, on a roof wash you may charge extra for a crazy pitch or different material. House washes may require special cleaning and care like cedar shake as opposed to vinyl.
Flat work may include flagstone, pavers, or coolcrete that can't fit in this model.
Here's the truth, you're going to underprice jobs from time to time.
You might even overprice from greed or ignorance. Eventually with time and research you'll find your scale and feel confident in the price/packages you offer. Don't sweat it!