There are many incomes, bequests, kingdom hall and branch sales, regular contributions coming in.
Then there are the expenses: in Europe a branch has calculated that each Bethelite requires around 2 thousand euros/dollars every month to provide food, accommodation and all the necessary services including expense reimbursements and monthly donations.
Then they have to support all the missionaries, special pioneers, circuit overseers around the world, some traveling by plane, others in cars purchased from the branches. They still have to print many Bibles and even some publications such as magazines, books and tracts and maintain printing presses. In the end what matters is the balance between income and expenditure which none of us really knows, but I know for a fact that at world headquarters they are alarmed by the chronic lack of funds.
I forgot among the many expenses there are trials, lawyers, television crews sent around the world, agreements for confidential CSAs and I'm sure I'm forgetting something, perhaps losses in bad financial investments