Federally, it is illegal to set a rate with clients. By law, rates must be negotiable. There's no regulation around sharing commissions between real estate agents, so maybe this is where you're getting confused?
This is why I keep using standard instead of law. Rates have always been negotiable by law but in practice they weren't. Oh well, not in this industry any longer so I'll just stay ignorant on this topic.
Higher sale price homes rarely use standard rates. Funny enough, you can pretty easily see this even on shows like selling sunset, when they show you the sales price and the potential commission. There's also points in the show where they explicitly discuss rates and points at which they negotiate it.
It's also super common to negotiate a rate with an agent if you're buying a new house and selling your old one, by offering to let them be agent for both.
Right but higher sale price homes aren't the ones that happen most frequently, which is why we have television shows around them. Completely agree with your last point, 1031 exchanges discounted even higher.