Definition:
http://dictionary.reference.com/browse/indicative
showing, signifying, or pointing out; expressive or suggestive.
From this definition indicative cost means suggested or approximate cost. The 'IMS' should be able to calculate this based on house design and features.
Final cost would be decided upon during the consultation.
This would be similar to MSRP (Manufacturer Suggested Retail Price) for a new car and the final price is decided by the car dealer.
I Hope this makes sense.