My first build, my bike
, wasn't bad since I've owned the bike itself for around 20 years now. The engine kit (66cc), speed carb, and 36T sprocket were around $200 altogether, from ZoomBicycles
. A few tools, and misc. bits and pieces probably added around $100.
For the second build, my wife's bike
, she bought the bike used from a shop for a bit under $100, the same motor, carb and 48T sprocket from the same supplier (bought off a neighbour who went and got it for his wife after seeing mine - she didn't want it so he sold it to me) for about $200.
I don't count the hours, because to me this isn't work.
For my current project, I don't really want to think about it. With the first two I had them both up and running within a weekend. This one has been an off and on project for quite a while now.