One of my suppliers responded to my request of making a discount with 'ok, for sheer cheek I'll give you a 5 % discount'.
I feel that it should be an idiom, but I cannot find it anywhere!
Are you familiar with this expression?
I don't think "sheer cheek" is an expression, but "cheek" refers to being very forward in a brazen sort of way. I would say that he respects you for being very assertive, and decided to reward you for it. If a child "gives cheek" to an adult though, he's being very disrespectful and might get smacked. Does that make sense?
And sheer is just an adjective. "I only made it out of that temple alive because of sheer luck." Think of it as more or less meaning "no reason other than".