More thoughts on possibly downsizing from an A to a B. But what we like about our A is the various sleeping arrangements. Tough to find many in the B market that offer true sleeping for 3. We are 2 ad...
I don't think diarz2's mileage is typical of Class B RVs. I consistently get 15 MPG with the Roadtrek (gas); diesel models are said to do better.
Not that many options for 3 in a Class B. Is a small Class C a possibility - one of the Sprinter-based models? Just from the floorplan, the Leisure Travel Vans Unity model, with twin/king beds in back and a dinette/bed up front seems pretty good for 3. It's over what the OP wanted to spend, but perhaps there's something similar in the used market.