Previously, it had been the fact that it shared so many parts with other vehicles in the GM catalog. With the new car, well, it's difficult to tell what is there and what is not, although I would expect some of the pieces to eventually proliferate to other vehicles in their next-generation models.
The C7, as it stands today, still offers a similar "tiered" level of interior trim like the C6 that can save a potential buyer tons of money. The standard trimmed model as a composite "leather" trimmed interior that isn't unlike what is currently used in the Impala, ATS, and other vehicles. You can opt up for the $8,000 "real leather" interior, but from what I can gather, not everyone will notice the difference.