1. Is this one on sale?
这个打折吗？
还能这样说：
Is there any discount of this one?
Any discount?
谚语：
One boy is a boy; two boys half a boy; three boys no boy.
一个和尚挑水喝，两个和尚抬水喝，三个和尚没水喝。
2. How much is it on sale?
打几折？
还能这样说：
What's the discount rate?
How much discount do you give?
谚语：
Much will have more.
越有越贪。
3. How much is it?
这个多少钱？
还能这样说：
How much does it cost?
What's the price of it?
应用解析：
make a price 开价，定价；
cheat at the price 物超所值
4. How much does it come to?
总共多少钱？
还能这样说：
What's the total?
How much will it be all together?
应用解析：
come to 还有其他意思：苏醒；结果是；涉及，谈到。
例如：She came to herself after being knocked down.
她在被撞倒之后苏醒过来了。