That's not even the whole story.
The new 2025 CT5 comes with supercruise as standard which was once a 3700 dollar option. This brings the price difference to 1000 dollars.
In addition the 2025 comes with the ultraview sunroof as standard while on the premium luxury it used to be part of a 9000 dollar package or a 1450 dollar option.
In addition the AKG stereo on the 2025 is standard where in 2024 you had to opt into the 9000 dollar package to get the worse sounding premium bose system.
Overall feature for feature the 2025 is actually substantially cheaper than a similarly optioned 2024 would be.
I can see why they slashed the prices on the CT5, it's just not a good seller in the market. We will have to see what this translates for the Blackwing. Given that sales aren't exactly brisk anymore with cars on lots and upcoming competition (new M5) I'd be surprised if it's anything more than a 1000 to 1500 dollar jump.