expression
a bit lower (price)
Used when haggling to ask for a further price reduction; literally 'one more voice', implying one more concession from the seller.
See also: もうちょっと
「もう一声いけませんか？」と値切ってみた。
I tried haggling, asking, "Can't you go a bit lower?"
彼は「もう一声！」と言って、さらに値引きを求めた。
He said, "One more reduction!" and asked for an even bigger discount.
もうちょっと is a general 'a little more' used in many contexts, while もう一声 is specifically a haggling phrase asking for a lower price.
From もう (more) + 一声 (one voice/call), literally 'one more call', used figuratively in bargaining to request one more concession.