"Well, what do you want? I haven't got all day." The Professor says gruffly.
You tell him what you need and he tells you how much it will cost.
"What, you thought it was free?" He asks irritably. "Potion components aren't free, except for the ones I gather myself and they cost time as does the creation of these potions. My valuable time. Oh, you can find it somewhere else less expensive?" He asks. "Then by all means, buy it there. Although I'm sure they are probably not a Certified Potions Master..."
[Note from the Potion Club: All money raised in this store goes toward funding Professor Snape's Alchemy endeavors. See his progress and visit Hogwarts in Towns at The Hogwarts Project. Thanks for your support! --Loch, Potion Club President]