Narcissists are known for their self-centered and manipulative tendencies, and their actions can be unpredictable and inconsistent. While it's possible for a narcissist to make grand gestures like buying an expensive gift, they may also use it as a tool for manipulation or to maintain control over a relationship. Their behavior can change quickly, and they may devalue and discard others without much regard for their feelings. It's important to remember that every person and situation is unique, and if you're dealing with a complex relationship issue, it may be helpful to seek advice from a mental health professional or counselor who can provide personalized guidance.