While it is not a Yamaha I bought a Sportsman 1000i from Amazon on cyber monday for $200 and free shipping. Only wanted it for charging the trailer batteries and it works great for that. Charger goes into bulk mode and it has a little bit left. Won't run the AC or microwave but for $200 it is a great little Genny and when the charger goes to absorption mode the thing throttles down quite a bit and is pretty quiet. Also only weighs 18 pounds.
Would I prefer a Honda or Yamaha? Definitely, and if I get a bigger one to run AC I probably would, but for battery charging? No need.