The reply for a situation like that is simple:
"People only value those things which come at a cost."
If you give something to somebody for free, they won't value it. Before long it will be piled up in a corner with all their other useless possessions.
But, if they have to pay for it, that very same object that was once given to them for free suddenly becomes valuable.
If somebody asks you for freebies and they aren't a family member or close friend simply tell them that.
(If they were a friend or family member they wouldn't have to ask. Would they? )
Again, there's nothing wrong with bargaining... nothing wrong with asking for a discount. No harm at all.
Neither is there harm in saying, "No." if you don't want to give the discount.