Loaded S4: 62,850
Loaded CTS-V: 71,870
So 9k, but the Audi has some features not available in the V, such as adaptive cruise and side assist (going from memory, haven't looked closely to see if 100%).
In my opinion, different price points even loaded out. Compare them equipped similarly and the price difference jumps up to closer to 15k.
Just priced one more frugally, 52,800. Fantastic price compared to the B6/B7 at same price for much less of a car.