We were 3 people and we covered mysore, coimbatore, ooty, kodaikanal and munnar 9 in days with 9k per person! which includes food, stay and traveling cost!
Kerala called as Gods own country, solo travel allows you to form lovely memories. For 5N 4D Kerala solo travel cost ranges between 8k to15k. Based on your mode of transport and place of stay, cost varies. Tripoto organises trips to Kerala, sharing the details just in case you might check in, see if it is suitable for your travel. https://www.tripoto.com/kerala/tour-packages/5-days-beautiful-kerala-12999-164510619915
Well, that really depends the way of traveling. I am going on a solo trip to Karnataka and Kerala in June and my estimated budget is approx Rs. 300 per day. But I also know a guy who travelled across India for 6 months in Rs. 2500.. I plan to do hitchhiking, sleeping in my own tent and eat at local food outlets to save on money so that I can travel longer. Also do consider Couchsurfing and Volunteering for a diverse experience.
It depends on your choice of hotels & for how many days you want to stay.
There are many good places to visit in Kerala & you can plan your stay accordingly.
For details click on the link below:
https://skysuiteshotel.com/places-in-kerala/