The excellent folks are SkateMetric (who do really good reviews) have done a blueprint and set of instructions for an excellent self-build they call their ‘Foosted’. It is using easily sourced components such as the Loaded Vanguard deck (but could use something else), Caliber II trucks, Wowgo battery and various components from Torque Boards.
I estimate for us to build this (to the same spec and parts list), sourcing as much as possible from European suppliers would cost us around £1200 (€1350). At that cost, you are getting better specification (motors and battery) than something like a Boosted Dual; however, a less informative remote (the LED display) and obviously no company to support you. It is not a clear call, IMO; I guess you build it because you want the fun of the project.
The Skate Metrics instructions are here: Foosted Build