5. I am sorry that we are unable to make you an offer for the time being.
很抱歉目前我們不能報盤。
還能這樣說：
We regret that the goods you inquire about are not available.
I am afraid it will be very difficult for you to get the offer now.
應用解析：
call into being 使產生，使出現，建立，成立；
come into being 產生，形成，成立；
in being 現存的，活著的

6. The offer is not workable.
報盤不可行。
還能這樣說：
The offer is withdrawn.
The offer is given without engagement.
諺語：
Blood is thicker than water.
血濃于水。

7. The price drop greatly on account of large offerings from other source.
由于來自其他方面的大量報盤，價格已嚴重下跌。
還能這樣說：
The price goes down badly, because there are many offerings from other source.
Large offerings from other source cause the price to go down.
應用解析：
a drop in the ocean 滄海一粟，九牛一毛；
at the drop of a hat 不拖延地；不遲疑地；
a drop in the bucket/ocean 滄海一粟；杯水車薪

8. This offer is subject to your reply reaching here before the end of this month.
該報盤以你方本月底前回復我方為有效。
還能這樣說：
This offer is open when your reply reaches here before the end of this month.
This offer has come into effect since your reply reaches here before the end of this month.
應用解析：
or nearest offer 或略低于此價；可還價；
slight one's offer 輕視某人的建議