Westfalias retail for upwards of ~$50,000, with 1980's models still fetching upwards of $15,000...
If the Elio [1] can retail for $6,800 new, it's not a stretch to imagine a modern minimal camper-motorcycle/tuktuk/scooter for under ~$20,000... models for countries with less regulatory requirements like India or Asia regions might have much less expensive versions.
[1] http://eliomotors.com/