这是最低价了.
I'm not kidding, but we are making a fair deal—30 yuan is quite acceptable for a decent man like you.
我不是跟你开玩笑.你是个体面人,30块的加钱很合理.
Do be reasonable! My offer is based on a minimum profit.
我这价儿不高,利已经够薄了.
It's the best offer I can make . Take it or leave it.
这是我能出的最低价,不要拉倒.