Eod1
If you see me running, I would try to keep up.
I used old antennas to cover the holes. They have o-rings to seal against the body to prevent leaks, and do away with the stupid plastic plugs that eventually weather and crack:
The large flat antenna is, I believe a GPS antenna that I used to cover the light-bar hole, which was about an inch in diameter.
This is on our 2012 Caprice 9C1, but I have similar antennas on our '10 Tahoe. Luckily, the Tahoe didn't have light bar.
But if you want to get rid of the holes, I pay the shop the $1500. It's a fair amount of work, if done right, and if done right, should be permanent. If they're planning on epoxying a piece of metal on the underside and then skimming the surface with Bondo, then, yeah, $1500 is way out of line. If they're planning to fit and weld in a metal plug, that's not a bad price, IMHO.
Until you find someone that thinks you bought your 2012 Caprice for the wrong reason.... LOL