If it's a bare bones model Z28 I'd say closer to 3,500 with the new ATS based chassis.
It has more to do with a mass produced car that they want maximum profits from. They could make it out of lighter materials but it's not cost effective. Also, a lot of federal safety requirements force things to be on the cars that weren't in the past (seat belts, air bags, ABS, ESC, TPMS, safety glass, crumple zones, side impact beams, roof crush standard, etc etc and next required on all cars by 2018...back-up camera's), and it all adds up in the weight department.