You are trying to describe two talking heads. Or One talking head.
Do not replace "said" with anything else that means basically the same thing.
Use adverbs extremely sparingly, it is far better to show some action that implies excitement, than to say "excitedly". This is somewhat an opinion, but an opinion shared by the majority of best selling authors. JK Rowling is an exception, she uses adverbs liberally, but then her books are intended for children that often need to be told what the characters are feeling, because they do not properly interpret the actions when shown what is happening.
Your scenes are under-imagined. You do not show setting, you do not show your characters interacting with the setting. The characters aren't doing anything as they talk, and it is seldom the situation that one person gets to have a complete monologue while the other person just sits like a lump and listens.
Far more common is the other person responding, verbally, or better yet, arguing, or asking questions about something they don't get, or not wanting to listen, or just not believing. They have body language: They frown. They look away. They realize something they had not understood. They shake their head. Roll their eyes. Sigh. Try to interrupt and fail.
The point isn't to add pointless "beats" but to make the conversation longer with more description, and more action.
If you watch a stage play, or a movie, you will seldom find actors sitting still and talking to each other in a room, they will have some "business" to do, walking around the room, doing dishes, drinking. There will be something going on the background that they are watching. The same thing for their monologues; watch for one-sided conversations on the phone for example. The camera is almost never on one face talking, there is almost always something else happening.
Most writing allows the author to reveal the thoughts and feelings of at least the POV character in a scene. That is something you can do, what is Sarah thinking and feeling during this harangue? Is she excited to get rich? Or has she heard this pitch from John a dozen times? When he says he's made people rich before, why doesn't she ask him, "Then why aren't you rich, John?" Couldn't she at least think that? Is she wondering how she can turn him down without crushing his feelings?
As a general rule in writing, find something for your characters to do while they are talking; that will provide the "beats" you are seeking, and they won't be empty, they will also increase the immersion of the reader in the scene, revealing the setting and feelings of the characters involved. And try to add conflict or tension to the conversation, disagreement, even friendly disagreement.
Why are they having this conversation? What does John want out of it, and what does Sarah want out of it? Would either of them rather not be there? John is clearly selling something, an obvious conflict is if Sarah doesn't want to buy it. Or does but cannot afford it. A less obvious conflict is if Sarah wants to buy it, but figures she can get something MORE out of it, because she'd be doing a favor to John by buying it. Is John desperate enough to add whatever MORE Sarah wants? Maybe she wants him to do her a favor, or she wants a bigger share than he's offering, or she wants a romantic relationship with John and this is a way to keep him on the hook.
More fully imagine your scenes, the setting, the sounds, the smells, the temperature, and the feelings and thoughts of the people in them. Are they fresh, or tired, or irritated, or happy? Even if those things are not explicitly written in the book, they would plausibly inform their responses, and it will make the scene more realistic.
Unless you are intentionally trying to create a surreal experience, don't ever write dialogue that might as well take place in a white room with nothing in it but the two characters sitting in facing chairs, spouting words.
