Tommy's 100% correct. French part design is a decade at least ahead of Puch stuff.
But really, the prices aren't that disimilar between Puch and Motobecane. It's just that you can get away with using a lot of used stock stuff in a puch, but a lot of people don't. If you step your game up both bikes you end with something very similar.
Puch
$125 = Ebay one speed
$40 = Super clutch
$125 = TR Crank+bearings
$300 = Gilardoni
$40 = 70cc head
$60 = Giant four petal reed
$110 = racing 21mm phbg
$100+$12beer money = Estoril, plus time and machinist fees to de-restrict it
$40 in sprockets to regear.
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$952
My 60mph motobecane
$150 = Av10 cases off ebay with cdi
$90 = Ebay four petal Polini reed plus new Adige cages
$80 = 19mm PHBG
$180 = Doppler pipe
$130 = Doppler Crank + Bearings and seals
$200 = 70ccH2O Malossi kit
$35 = Honda elite 125 radiator
$80 = Doppler ER2 variator
$4/wk = 4l320 belts
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$945
End result? Moby blasts Puch, is quieter, climbs hills, looks cooler and goes really fast. What else do you need to know?