I think I would try to find some clinic that will take you on; free, reduced rate or payment plan. I think it needs to be looked at and I think the question you should be asking is not can I afford it but can I afford to lose my vision or my eye.
A doctor, even if he is unwilling to treat it, should be able to give you some idea of what the growth is and what kind of prognosis you might have with having treated or untreated.
As a diabetic, you are already at risk for vision issues. I think a frank discussion with your doctor is in order.
Good Luck.