If you want to help someone pay their GMAT exam fees, you can actually do this by buying them a GMAT Exam Gift Voucher. These are available from the GMAT website and cost $250 - the price of an exam.
Vouchers are non-refundable and are valid for 5 years from the date of purchase. They cannot be used to pay for an exam that has already been booked and cannot be bought in the European Union or Japan.