At that price tag I see it competing with used cars. If you are looking for cheap transportation you can get a used car in a decent condition for ~$2000. That would leave you with $4800 to spend on gas. According to the EIA the average household spends $3000 on gas per year. Dividing by two and assuming two cars and two daily commutes, the $4800 would only last for around three years.
So that means that it would take three years for somebody to break even and start saving cash on gas if you decide to go with the Elio instead of a used car.
So whether this concept will sell or not depends in part on whether the customers will view it as a long term investment or a short term fix until they are better off financially.
And I really don't buy their second commuter-only-car pitch. Somebody who can afford a new $20K vehicle can also afford the $700 (they claim $800 in gas per year) yearly penalty on gas, so the only people I see being attracted by this concept are people short on money which probably drive used cars.