I did an 80s Cannondale SR900 bare-metal refurbish from a frame/fork that were free. It only cost me about $400, but again, the frameset was free, and I also used a ton of stuff I already had (crankset, brakes, seatpost & saddle, front wheel, and tools!).
So the $1,300 cost for the Schwinn rebuild sounds like a lot to me, but it always depends on your starting point, and whether you repurpose things or purchase everything specifically tailored for that build.