The number in question is vehicles sold, so the only relevant brands here are Volkswagen and Audi, really. Toyota also has Lexus and Scion.

The cheaper European brands like Skoda and SEAT also likely have significant volume. Skoda, for example, sold over a million vehicles—a non-trivial 10% of VW group's total.

Audi sold something like 1.8M, probably with better margins than Skoda, so it's certainly a more important brand, but SEAT and Skoda aren't trivial either.

Just in terms of car sales, SEAT + Skoda ≈ Audi.

I'm interested you call SEAT and Skoda cheaper, I'd label them mid-market.

Seat and skoda are only popular in handful of small European countries, vw is popular around the globe.

If we could buy Seat and/or Skoda in the states, I bet they would sell rather well. Kia and Hyundai are no longer "bargain" vehicles as they were in the past.

Skodas are quite popular in India

there aren't many cars in India compared to US or even some small European countries.

The brands that you are dismissing out of hand sell, in aggregate, several million vehicles per year worldwide. That definitely moves the needle.

You are ignorant. http://apps.who.int/gho/data/node.main.A995

India 159m, USA 265m registered vehicles. India is the 6th largest producer of vehicles.

Vast majority of those are 2 and 3 wheelers, we are not talking about those.

SEAT does pretty well in Mexico.

Not any more, Scion was shut down as a failed experiment last year.

Skoda as well - (a million cars a year)