In short yes, there is a substantial price differential in painting the exterior of mobile home. There are a variety of products on the market today for preparing the metal surface (usually aluminum) after which a traditional paint product for exteriors can be used, and as with painting any metal surface an oil based product should be used. I reccomend asking your local r/v supply retailer which primers they have in stock and count on an additional 20% in materials over what you would normally pay to paint a wood surface.
It can be. Pricing is relative to the material you are applying the paint to and the type of finish you’re after. A way to illustrate is like a bright, shiny finish on a metal car or a dull, rough finish on a concrete wall. Although a home may not have these extremes, it’s still relative to the product and the surface. Any good painter will want to look at the job before giving a quote.
This would depend on the prep you have and the detail involved with the color scheme. Some mobile home parks do not let you spray in the park, so the time it would take to cut and roll versus masking and spraying would definitely vary.