Please correct me if i'm wrong, but I think the comment was suggesting more than the fact that Tesla, in the literal sense, sells more than cars. I think it's also important to note the company itself supposedly operates much differently than a traditional car company, and in fact much like a software company.

People aren't buying Apple stock because of what the company is today, they're buying it because of where they think Apple will be in the future relative to what they are now. In Apple's case, that future version might still be a consumer electronics company. Just one with (hopefully) innovative new products and a higher share price than you're buying in for.

Given the Tesla's SolarCity merge, the associated solar shingles project, the battery gigafactory, the PowerWall, and their grid energy storage projects, I wouldn't invest in Tesla today thinking "Tesla is a car company, and 5 years from now they'll be a bigger car company with new car models!" in the same way that I'd approach Apple.