...Seems like the price of donors is everywhere when it comes to the SS's. Bases are a little more common to be cheaper. When I was considering my build I would have preferred the Turbo, but, it was more expensive and then the kit was also more expensive. I rode in the supercharged one in TX and knew it was fast enough for me. Just about any of the donors have potential as we've seen here on the forum.
If you have a selection of donors nearby you may consider thinking about what it would cost you to upgrade whichever one to were you think you want to end up. For me, I knew if the supercharged one wasn't enough power I could pay about 450, and get a stage 2/3 zzp kit.
So...If the base isn't enough, I think you can get a supercharger kit for 750 + the cost of the supercharger. so somewhere around 1k...maybe more depending on what all you can find 2nd hand...
https://zzperformance.com/products/2-2-2-4l-bolt-on-supercharger-kit
Luckily for us there are a lot of Cobalts made out there. The facebook groups always have superchargers for sale.