First, welcome to Air Forums. Lots of good information here.
The biggest cost of ownership is in such things like fuel, fees for parks, tow vehicle (TV) expenses, insurance, taxes, and of course the depreciation factor when one either grades or sells the unit. And, these are all quite variable.
What TV do you have? How many miles will you be towing each year? Where are you planning on going?
Maintenance on an Airstream, new, is not very high but a lot of us find all sorts of things to change....
Anyway, we will see who adds to the confusion shortly as far as cost of ownership is concerned.