Depends. If the quest giver names a specific monetary reward, then it invites for negotiation. Which can be fine. The negotiation can both be used to portray characters and get a hint if there is something fishy behind the offer. But players will need a reference as well for the negotiation, like “she offers 100 gold coins which is more gold than any of you have seen in your life”. Make sure to communicate this context as well.
Another option is to not quantify the reward or to offer a reward that is not money. “She promises that you will be princely rewarded.” Or “You can pick the finest horse from the king’s stable.” These are more fun IMHO. You can tie the reward in to what the characters dream of besides a boring “get rich”. This then can also be a negotiation in game (between quest giver and pcs) or out of game (between GM and players).
“I have this crazy fun adventure I have prepared where you will be travelling to this mystic place, what would make your character accept such a quest?”