An example for difficulty for gutter cleaning: There are lots of variables for gutter cleaning, the one that stands out is the number of stories on the house. Difficulties go further than one variable, a couple variables you could run into are the cleanliness, how clogged the drain is and the terrain the service pros are navigating throughout the service.
My crew is paid at a generous hourly rate. To perform well on our price sheet and make our price model needs we need to have the price of the bid cater to the crew's pay. The time is a big factor on the amount you are paying.
An example for a type or model for windows: cleaning windows can vary depending on multiple factors. The most common of these factors are the shape, height, and angle of the window. We love cleaning all windows- but if your windows are unique and difficult to clean, it may factor into the price.