Apartment Interior cost

I am having an under-construction apartment in Bangalore and they will handover for interiors in June 2026. Most companion in Bangalore charge exorbitantly is what my friends and colleagues say and most of them got the interiors done from their hometowns ( like Andhra /TN ). I am coming to Kerala for a month and will be in Trivandrum and Ernakulam for 2 weeks each in my hometown.

1. How much does interiors cost for a 3bhk 1200 sqft apartment
2. Does it make sense it do it in Kerala and then transport and assemble in Bangalore.
3. Any spefic references that can help including past learnings

My primary requirement is functionality and good quality stuffs and not looking for aesthetic appeal.

I know the rates fluctuate a lot based on materials etc but still want to know an estimate.