お忙しい中ご連絡いただきありがとうございます。
合計○○ドルですが少しだけ安くなりませんか?
ご検討お願いいたします。
Thank you for contacting me, I know you must be busy. The total price you have put forward is $○○ but is it possible bring the price a bit lower? I hope you are able to consider my request.