"So ... I'd be camping for about 14 days in any kind of weather with a charging cost of 6 times $1.75 equals $10.50. Not bad."
You said up to 10 hours to charge, not me.
But either way, using a 45 amp charger, with the voltage to get the job done properly in cold temps, it would cost less than a third of that, so about $3.00 in gas... not to mention:
1) less than a third of the hours on the gennie,
2) no need to charge with the huge coach engine to achieve a full charge
3) the added cost of gas to run the coach engine
4) the added wear and tear on the coach engine
All said and done, about 1/4 the cost in gas, and at least 3x gennie life. No tricks, just simple economics.