There have been half a dozen references to using solar/battery bank to obtain spot usage of a/c. Thread in Grey Nomads forum stated they are getting a/c equivalent to a DOMETIC which uses over 1.5 kW with a Fujitsu split/level which costs $700 and uses 750 W.
As far as costing big bucks just consider spending $0 for 90% of 365 days of boondocking. Further, do not buy an ATV, motorcycle or Waverunner and you have
Paid for a first rate system. Or buy a used pickup instead of a new one and get two first rate solar/LFP battery pack
Reed and Elaine