Yes Dogcatcher there was a lot of that "shipping overseas" going on during the late '50's & thereafter. When we returned much had changed and disappeared....
I seldom utilize cost/ benefit considerations in my bike building processes, but last night I did. Costs are approximate. Using the Predator 212: motor $130. shipped, ARC billet flywheel $130., Mikuni carb (real) $100., 3-D clutch $230. total basic parts = $590. not including misc. parts, shipping & any taxes involved. What you get 6.5 hp plus ? & single speed that will readily fit some smaller frame bikes.
I next looked at the cost involved in using the Honda clone 125 cc 5 speed engine which I utilized for both my Simplex & Harley "Peashooter" builds: Base engine shipped $375., Mikuni $100., CDI & electrical set $60., plus additional shipping & tax. Total basic parts=$535. What you get 12 hp, kick start, 5 speed integrated transmission, 10,000 rpm & a wet clutch.
I'd say cost /benefit are obvious, but will readily concede that the frame construction/alterations are more difficult to fabricate, but not necessarily more expensive dollar wise...time wise yes.
I'm still going to build a 212 Predator in the future, like I said I seldom use cost/benefit calculations in my builds, but the 125 cc still stands out in the comparisons. Rick C.