Cremation is the process of burning the dead body at very high temperatures and finally the ashes are retrieved (remains of the dead body) which is then used for various rituals. Every community of people have their own way of cremating the deceased person.
For Hospital based deaths the hospitals provide the Death Certificates before cremation and for all other cases (non-hospital) you can get the body cremated and then get the death certificate from the local government body.
Just doing cremation in the crematorium varies with each local body of the government as low as 200rs to 2000rs (Few of the Local Govt. Bodies also give free cremation services), other activities such as transportation, pujas & rituals etc. will be added to this cost.