Has the rate/price of potatoes gone down? / Has the potatoes become cheap?

[Tait-ka]

Yesterday I went to a vegetables shop to buy one kilogram of potatoes. The shopkeeper gave me one kilo of potatoes for Rs. 60. I bought one kilogram of potatoes from the same shop for Rs. 100 three days ago.
I asked the shopkeeper, "Has the rate/price of potatoes gone down?"/ "Has the potatoes become cheap?"

(SELF-MADE context. But note that the bolded sentences is how people talk to shopkeepers here in Pakistan. The bolded sentences are literal translations of what people say in Punjabi/Urdu here.)

Are the bolded sentences natural/idiomatic?

 

[jutfrank]

This is what you mean:

Has the price of potatoes gone down?

 

[Skrej]

I might also ask "Oh, did the price of potatoes drop?"

 

[Tait-ka]

Has the price of potatoes gone down?

You mean the above sentence is idiomatic of the choices I've given?

 

[jutfrank]

The word 'rate' is the wrong word. The verb 'has' agreed to plural 'potatoes' is ungrammatical. The reference word 'the' is probably wrong in the context. The verb phrase 'become cheap' is evaluative and not synonymous with 'price gone down' as well as seeming inappropriate to the situation.

Remember that if you want to ask us how to express something said as part of a conversation, the way that you phrase a thought depends on a multitude of contextual factors, including who you're talking to and why, what tone and attitude you want to take, what you want to focus on, what kind of response you want, etcetera.

Why would you ask the shopkeeper if the price of potatotos has gone down when it's plainly obvious from the situation that it has? Are you trying to show surprise? Or approval? Or confusion? Maybe you're trying to suggest he overcharged you previously. All these things matter to the way you phrase something so you should tell us this in post #1.