Firstly imma Brit so my prices are different
But my first Puch Maxi was £140 needed a full rebuild.
At my latest invoice count I’m at around £1800 but my bike is quite fast and I’ve bought somethings more than once as I’ve developed the bike further and further.
I would think for around £100-150 you can rebuild a stock bike with an aftermarket crank and replace all the parts below and have a really reliable bike.
you’ve got everything that moves to replace plus seals, headset bearing, wheel bearings, tyres, tubes, cables (maxi has 4, speedo,starter, front and rear brake) crank, seals, sprockets, chains, gaskets, possibly brake pads and clutch pads also.
That’s before performance modifications.
but For £2-300 you could rebuild a maxi with a few performance parts and easily have a 40-45mph round city/town ripper!
Or for £1000+ a 60mph bike is possible
It really depends what you want and if you’re doing this hobby for yourself or to compete with the next guy a 25-30mph stock bike may be all you want.