I figure my generator costs in a different way.
To run my Onan 4kw, depending on the cost of fuel (gasoline)
It costs between $.80 to $1.40 per kilowatt hour based on a 3000 hour lifetime of the generator including the purchase cost, maintenance, repairs, and fuel. That figures using fuel at between $2.25 and $3.25 per gallon.
When in use, I figure loading the genny between 2 kw and 3 kw. Less than 2 kw would be more, more than 3 kw would be more.
Depending on where I am, when I pay for it, electricity usually costs me between $.10 to $.20 per kw/hr. So, using the genny is very expensive compared to plugging in, but hey, ya gotta do what ya gotta do. With that in mind, paying a daily campground rate of +-$25 seems like a good deal if electricity is included and it's hot/cold outside.
Chum lee