英语翻译亲爱的朋友:上次的20件的价格是因为我的失误,赔钱卖出,为弥补对你的损失,希望你能体谅,你是我的好买家,我想维护

dear friend,
For last deal's 20sets,I short quoted you by mistake and that won't cover our expense,hope you could understand.You are a nice buyer of mine,and I want us have a long last cooperation.Now you mentioned that the price is too high,let me give you a final price,300usd.
waitting for ur comment,thanx.