You are comparing to different segments.

Sandero is 36 cm longer, 27 cm wider, 2 cm taller, and has 28L more of the trunk. So the difference will be even bigger.

For 20k you get Jogger, which is a wagon, even more space, and it can be a 7-seater.

And also real life range of Dacia Spring is around 160 km. So that is very little for 20k .€

Talking about Sandero, comparable in size Renault ZOE starts at 37k €