客户要求afterpayment,付款方式谈不拢，还有争取的必要吗

上邮件先： 客户： Our current distributor keep parts in our wharehouse about 40 000USD value and we he afterpayment method, that means we pay only after our client is already paid us. 我： sorry but afterpayment can not be accepted. We're a company with our own factory, thus to guarantee raw materials and normal production, we need to ensure the stability of our capital chain. So 30% prepayment and 70% of the balance 7 days ago before delivery is our bottom. Thanks in advance for your kindly understanding. 客户： I`m sorry, but I can not accept this, because in my business it would be a step back. I hope you understand this and it doesn`t cause big problem for you. 我觉得这个客户这么要求简直是很神奇的事啊！我觉得没法谈下去了，还值得争取么？