We often have promotional offers on products. To claim the promotion:
1) Make sure the products selected are relevant to the promotion.
Example: If there is an offer to buy 3 blog posts and get 20% off a third, you must have 3 blog posts in your cart.
2) Click the ‘Offer’ button and the discount will be automatically applied.

Outside of promotions there is no facility to negotiate prices with Sellers. Their price is fixed.