when considering a piece of equipment on an auction that  says it 'needs an engine'  and  everybody can see that the tracks are shot,  missing the door,  and has no  bucket  (CTL machine here)  

 I  added up  putting in a new engine,  new door, bucket,  tracks and probable  idler wheels/bearings and a new seat.
Plus a few  extra thousand for incidentals for a total of 18k for parts.   Zero allowance for my time.

Now,  the exact same machine, in running condition,  probably  2000 less hours  brings about  28-32k  all day long.  
knowing these 2 values,  what is the  go, no-go  price here on the  subject machine?   

Is the value of the rebuilt machine going to be the same as the good runner,  (my luck has never  paid to fix anything and expect a premium over  something still running) 
I certainly don't pay a premium for  someone elses  rebuild.     It either runs strong,  or it doesn't..  and I pay accordingly.
 
long story short,  my 'max bid'  was  blown away in the last minutes  by several thousand dollars.  
Should I have  valued  of the finished rebuild project closer to  40k,  with a lot of brand new parts... or  the  25k  'good runner' that could blow up  hours  after trailering it home?