A economic charango is not bad it all,the sound and construction quality is not scrifice.The main difference is in the wood that is use,like:

soundboard can be in 2 pieces of wood,like a classical guitar,but very stable.

fingerboard will be in indian rosewood or jacaranda,which are very good too(stable).

soundbox can be in naranjillo or sotomara,naranjillo is a native wood from Bolivia and sotomara is like caoba peruana or the honduran mahogany.

Is economic because take less time to build it and don't have too many details in the construction,and the labor cost is cheaper,but again,has a great sound,intonation and craftmanship.