Its not just the money, but the overall time and effort to do a restoration, a custom or a resto-mod right. If its going to be a weekend driver and not a show queen looking for awards sure a engine trans, suspension upgrade and paint is a nice project if you have the time to do it and a place to do to. But an actual show car looking for authentication awards like a NCRS award for Vettes or the ,Mustang Club of America (MCA) or the
Shelby American Automobile Club (SAAC) or the numerous National roadster and custom car shows, like the Ridler for example, you had better have some deep pockets to get the job done right. So that new manufactured Chev, Ford or Dodge is a steal as compared to spending the time ( years) and money to build something to compare. . And a new "muscle car" comes with a warranty, and most likley AC and all the new safety things