This is a jaw-droppingly horrific system you're imagining. Amongst other things you've effectively insulted rich criminals from any repercussions, and basically given them a slave underclass (please, no snarky comments about current justice system). Do you genuinely think this a good idea?
Our current legal system has evolved over many hundreds of years. I merely describe a set of initial conditions and a few possible early developments. The space of things it might evolve into seems pretty wide. I do suspect some of those things would be good. That said, in the meantime:
Also, this doesn't insulate rich criminals from all repercussions. If they have enough money to pay the fines when murdering tens of people... well, you could try killing the criminal directly. You can do that today as well, if you're prepared to pay the price.
A really rich criminal could hire bodyguards, of course, but those would be costly, imperfect, and have some chance of turning against their employer. Ultimately it would become a rich guy in charge of an organized criminal gang, which... is also something that exists today.
We know how this goes, because forms of it are what the current system evolved into; there are obvious descendents of what you say in the legal system. But that doesn't mean applying it literally, as with your "early developments", wouldn't have awful consequences.
> ...If they have enough money to pay the fines when murdering tens of people...
It's not about "murdering tens of people". It's killing someone whilst drunk driving, or murdering someone in an argument. These situations clearly still happen in the current system. But with what you're saying codifies that, if someonene is rich, as long as their crime is not against someone else rich, they can generally avoid any repercussions. Blood libel is still a thing, can literally see it in action in countries which have legal systems that allow it.
