why they charge 50$ on 125$ worth of bitcoin
and 50$ charge on 20,000$ worth of bitcoin
is because rich look after the rich, always have always will
No, it's because the bandwidth, storage, and processing costs that the miner has to pay (and therefore be reimbursed for) are exactly the same whether the transaction is for $125 or $20,000.
Bitcoin is not suitable for microtransactions and was never designed or intented to be.