Alto is a crap car... No road grip, no comfortable drive and it's so small. It's just like a mehran with better looks and a good ac. However it is cheaper to maintain and has good resale.
Santro is a much better car with an EFI engine, nice interior & exterior, more space inside, better road grip and more confortable drive. The santro club gv or exec gv also comes with good boot space as the cylinders are fitted under the boot space.
It is a bit expensive to maintain but if you get a good condition santro, you wont have to visit workshops too often. Resale is also not bad these days.
Yes you can get a good santro between 500-550k