While that makes sense, the claim of the article is that car prices are rising relative to household income -- in other words, it implies that the average new car used to be affordable, that it now is no longer so, and that it's continuing to become increasingly unaffordable.
Actually, car prices have been increasing at a MUCH lower rate than inflation or other costs due to automation of factories, better designs, electronics prices dropping, etc.
For example:
In 1996 I bought a NEW Honda Accord for $22,500
In 2015 you can buy a much better equipped Honda Accord for around $25,000
That's a 10% increase over 19 yrs! It's actually a decrease in price if you consider what you're getting for the cost (i.e. much more HP, MPG, safety, etc)
For reference...in that same time period, movie ticket prices have doubled, gas prices have tripled, housing prices have doubled.