Firstly, the hostel fees at BHU vary from course to course. So all I can do is give you a rough estimate through the information I got from my sister who pursued B.Sc from BHU.
Hostel Fees
Mess Charges:
Usually, there are 2 diets a day and on Sundays, there is only one diet. But the Sunday meal is special so it is counted as a double diet. So the approximate price stands at INR 80-100 per day.
If you skip the meal or go home then you can tell Mess Maharaj and you won’t be charged.
BHU hostel fees are INR 4500 per year. Mess fees aren’t included in the above amount. Mess fees are calculated per meal. A typical meal costs around 40-50 rupees and usually meal prices range between INR 40-80. Which rounds up to around INR 2500/month. So, including the mess fee, you will be spending around INR 7,000.
As my brother used to be a student there, so let me answer this with whatever I got to know from him about the institute.
And, with the exception of IMS and IIT hostels, I believe that this estimate may be applied to practically all BHU hostels.