Who do you think spends more? Your neighbor vacationing a few hours away from home? Or that international visitor who wants to see everything they can in their one week in the country?
So let me get this straight. Foreign tourist spend less money in your country than domestic tourists because the foreign tourist are driving in with an RV and living off of a fifty pound bag of rice during their vacation?
Fwiw, there are a lot of highly frugal people in eg the surfer/kiting community (example!) which do indeed spend pretty much nothing where they're visiting for their hobby.
And they do often smell and leave trash behind.
So I can imagine that being true if you're living in one of those hotspots... It's a hard topic though
Let me set this straight: My point is you have an incorrect idea of how much space a month of food (and it needn't all be rice; that just illustrates the point) takes up. You can readily fit it in an RV, especially a big one.