Stubborn Eno man

A man walked into the pharmacy and wanted to know if we sell Eno. I told him we don't sell it. He asks me how much it would be?

From the top of my head, I said it should be less than $10. 

Him: How much exactly?
Me: I don't know because I don't sell it here.
Him: Can't you search up the price?
Me: I can't because each chemist sells it for a different price.
Him: How much?
Me: Less than $10.
Him: What's that mean? That could be $4 , $5, $9 ...... that could mean anything
Me: I can't tell you the exactly price because each chemist charges a different price, but it should be between $5-$10 from memory.
Him: No, you said it was less than $10.
Me: Yes, its between $5-$10.
Him: No it should be between $5-$9. It can't be $10 coz you said its less than $10.
Me: Well, if its $9.95, that would be less than $10.... 
Him: But......
Me: Look sorry sir but I really don't know the price. Its best to ask a chemist that actually sells it. If you don't mind, I gotta help these other customers here.


Waste of my time.