Machine work progressively replaces value in the reproduction of labour-power to restore periodic profitability, capital hoards this productive capacity.
Once you recognise the machine’s metabolism, the variable isn’t labour. Labour is only ever concrete labour, the magnitude of machine work reducing concrete labour in the reproduction of labour-power is the variable.
The capital required to create the machine is created out of thin air by banks - on the proviso future sales pays it back. Once the capital is repaid, capitalists literally get free stuff to sell.
If Marxism is dialectical materialism, then how does machine work become unpaid labour time whilst never breaking Marx’s axioms plus the scientific axiom 4.?
1.Labour = human work specifically: Capital Vol. 1, Chapter 7: