Resto costs
It's actually pretty easy to spend $20K on body work. Let's say the shop charges $60/hour. $18k is 300 hours or 7.5 weeks working full time. How long does it take to strip everything single nut and bolt off of a car, including suspension, all trim/glass, every bit of that the asphalt damping material, etc. And, assume it's done carefully, not breaking things, labeling, bagging and photographing for reassembly. How long? I'd say at least 50-60 hours. Then you have to get the body stripped to bare metal, and straighten and fix all the dents and dings. Replacing a quarter panel is already 30-40 hours if you want to minimize the use of bondo/lead and replicate all the factor spot wells properly .What if you have to pull the door or hood skins to address some seam rust? I could easily see 3 weeks burned up with this phase. So now you're at close to 200 hours and you've not got any paint or reassembly. For a car that needs a moderate amount of rust and body work, a nut and bolt restoration of just the body should take 400-500 hours.
I think $80,-$100k is about right for a full on, ground up restoration to show condition.
John