I bought a used Honda EU2000I Companion for $600, ran it for 4 years, and sold it for $750.
Try that with your Champion. I've no idea what the used market is for them, or resale value.
BTW, at 1200 ft elev, temp 83 F, and fully charged batteries, my Kill-a-Watt meter says that my Dometic pulls 13.1 amps, with the 22" LCD TV going also, the charge controller drawing 1.2 amps with the A/C off. So that is about 11.9 amps by the fan and A/C running. It did not start the A/C the first attempt, overloaded the genny, but it did start it the second attempt. It will run on Eco mode, and the RPMS will drop I am estimating about 15, maybe 20%, once put in Eco mode. Took about an hour to pull the temp down to 70 F inside. Once started the Eu2000i is not working too hard if your batteries are in good shape. A little starting help from an inverter off your battery, say 1000w worth, would make things start a bit easier. So would temporarily pairing another Eu2000i or 1000i, just to get the A/C going.
BTW, I burned about 20% of a single tank of fuel doing this, two Eu2000I's will loaf in Eco mode running the A/C if paired, only revving up to handle A/C start up.
The Gen I ran the gas through today , with Techron and Stabil Red, 1 oz to 2.5 gallons, seems to run a lot stronger now with some serious running time on it. These generators just need to be run under a good strong load from time to time, to flush out the gunk in the jets in the carb, to keep them running healthy. YMMV...