There’s a saying that clients can have good, fast, or cheap. Pick two, but then the third will be whatever it has to be based on the other two choices. You can have good and fast if you’re willing to spend a lot of money. You can have fast and cheap, but the quality will be poor. You might even be able to get good and cheap, if you’re willing to wait a long time.
A variation on this theme is the iron triangle. You draw a triangle with vertices labeled “features”, “time” and “resources.” If you make two of the sides longer, the third has to become longer too. Here goodness is defined as a feature set rather than quality, but the same principle applies.
There’s a problem with this line of reasoning: no matter what clients say, they want quality. They may say they want fast and cheap, and if you tell them you’ll sacrifice quality to deliver fast and cheap, you’ll be a hero — until you deliver. Then they want quality. As Howard Newton put it
People forget how fast you did a job, but they remember how well you did it.
Sometimes you can cut features as long as you do a good job on the features that remain, but only to a point. Clients are not going to be happy unless you meet their expectations, even if those expectations are explicitly contradicted in a contract. You can tell a client you’ll cut out frills to give them something fast and cheap, and they’ll gladly agree. But they still want their frills, or they will want them. The client may be silently disappointed. Or they may be vocally disappointed, demanding excluded features for free and complaining about your work. Eventually you learn what features to insist on including, even if a client says they can live without them.