It is about land values to start with, then about the cost of building and maintaining the facility.
I pay $66 a month for covered open storage in a formerly rural area that is starting to be more developed, within city limits of a declining small city (all the biggest employers moved to bigger cities). A spot in the open within 20 miles of Tulsa (or one of its suburbs) is going to cost $120-150. So $120 near KC doesn't sound all that bad.
I don't like the storage to be more than 3-5 miles away. As it is, I put on almost as much miles to-from storage as I do going house to campsite, which is about 15 miles for me.
In a severe storm area, I'll pay whatever is needed for covered storage. In this part of the country, enclosed and climate controlled is not such a big deal, my concern is the frequency of "golf ball size" or "baseball size" hail. Other locales have different problems (think 200 inches of snow).
Storage is just one of the costs of RV ownership, about on a par with insurance (for a motorized RV, at least) but a small fraction of value of money costs (depreciation, interest, loss of investment income). RV owners tend to ignore these bigger costs, which they don't easily see, and get hung up on the smaller costs for which they have to write checks monthly, quarterly, annually etc.