Hi Mr. Wizard,
600 watts of solar is about $2 per watt installed (DIY). A decent inverter is a further $400.
Any boondocker is going to have a larger than average battery bank, so I don't see that as an additional cost.
Propane is an ongoing expense. Solar is not, other than the lost interest on the initial cost.
Then, as you know all too well, from personal experience, there is the unreliability of absorption technology. I hate having to level the RV in the parking lot when I stop for groceries.
When I was NOT full time I did run my absorption fridge on 120 volts. If I had a residential it would spur me towards increasing my solar harvest.