how shall we make a clear and accurate offer an counter-offe

First we should calculate exactly the cost price of raw material of the items the customer need.
And then we have to count how much the money for the workers to fix it or pack it .The last the freight to the destination is also needed .After all these ,we have to add the profit we must earn .Then we send the customer a clear offer .If you get an counter-offer later.you can contact with him for discussing about the price and delivery time and the payment.

我们怎样做出清楚且准确的报盘和还盘？

By cash.