That’s not how PoS works.

So tell me again, how much money do you need in order to stake?

0.01 ETH or less, through decentralized staking pools.

But your main argument is wrong: validators do not control the network. Users running node software do. Running a node is free. If a single validator began to exert unwanted control, the honest majority of non-rich users could slash or evict them.

What prevents the rich validators from slashing non-rich users so they don't lose their majority?

It’s not the majority of stake that controls the chain, it’s the majority of honest users. Rich validators can collude to have 51% staking power and start to exert unwanted force, like censoring blocks for their own profit or doing something else unwanted, but the majority of honest users can decide to coordinate a soft fork and point their clients at a new chain. The controlling validators will only be rich on the old chain.