5. I think you've overcharged me.
我认为你多算了我的费用。
还能这样说：
I think this is more than the real bill.
I don't think I spend so much.
应用解析：
overcharge的意思是：索价过高;使过度充电或装填;夸张。
例如：It's a poem overcharged with emotions.
这是一首感情过于丰富的诗。
6. Your total is RMB 150.
你需付150元。
还能这样说：
Your meal is RMB 150.
You should pay RMB 150.
应用解析：
total还可以表示：使完全损坏。
例如：His new car was totaled in the accident.
他的新车在车祸中全毁了。
7. Let's go Dutch.
我们各付各的吧。
还能这样说：
We each pay our own bill.
We pay separately.
应用解析：
Dutch courage 酒后之勇;
talk to sb. like a Dutch uncle 严厉地告诫某人;
do the Dutch 逃走;自杀;
in Dutch 碰到麻烦，处于困境
8. This is my treat.
我请客。
还能这样说：
I will treat you.
I am buying tonight.
应用解析：
go on a fair treat 进步很快;
stand treat 负责请客的费用;请客;
treat oneself to 舍得(吃、穿等);
treat of 论述，论及