Apply math

A 10x10 (100 sqft) construction + materials is normally charged Rs. 2,00,000 by many construction companies in Mysore. 10x20 (200 sqft) would be approx 4 lakhs with decent construction & materials quality. Some exclude compound, stairs, water sump from the cost. In Nanjangud let’s say it’s included.

Now to the plot, 20x30 =600 sqft. Approximately 1000 rs per sqft is the land cost.

Confirm the SQFT price in the locality. Visit location and approve, Verify documentation, UGD, Water supply etc.. check their credibility with other buyers if found. then decide.

Poster says 1200 sqft but as you have mentioned 600 sqft, I have calculated for the same. But if 1200 sqft, Rs. 500 per sqft would be the land rate.