It used to be 100 rupees per month when I used to learn, but that was around 15 years back.
These days it is around 500–600 rupees per month if you are enrolling for the normal, routine classes which is generally in the morning. It also depends on the Kalari; some of the high profile ones charge in the thousands.
It also depends on the location. The ones in rural areas are generally cheaper than urban ones.
If it is a crash course that you are looking at then again the cost would increase.
In any case it will not exceed your general gym membership fee.