Strange, but it usually feels like it's just the other way round (tough usually with NPCs):
NPC: bring me <whatever>
After accepting the quest I usually end up ploughing through an army of monsters until I finally find a <whatever>.
I return to the NPC and claim my reward.
NPC: Thanks! here ist <ridiculous amount of gold which does not even cover my blacksmith bill> and by the way, our relationship maybe neutral now but bring me a gazillion more <whatever> and I may consider you exalted and sell you one of my <real cool purple stuff>.
If it comes to players at both ends I guess I'm just in a rather nice guild who are always ready to throw potions, gems, enchantments, food and whatever I might need at me without expecting to get paid and usually so do I.