Workers are free to collectivise, in fact encouraged to collectivise, as collective bargaining CAN BE (not necessarily so) an efficient process in the free market, i.e. as many players are allowed to express their value, and employees employ a fair labour product.
. However as every individual is unique, the most ethical, would be to have individual agreements.
So sadly a collective price = always being a FAIR practical consensus, although a sub-optimal consensus for some (talented?) WORKERS at the expense of their dumber mates. But if that HERD mentality works for the productive worker, then so be it. The SLAVE mentality is likely to be, by its nature - unproductive. Any collective employer MUST factor in the risk of dumb/unproductive labourers and so reduce the price of that unproductivity AND the price of that RISK in any collective agreement.
Subject to:- Known market failure i.e. were a collective bargaining is inimical,
i) to the degree that that other factor of production EMPLOYERS are allowed to form a MONOPOLY as well.
ii) for being against public interest. Contra bonos mores that is:- EXTORTION employees may not seek the worth of the economic (positive) externality that extends beyond the worth of their own labour, as they do when say e.g.
The power utility workers seek to switch the grid off
OR
The warffies stop the entrance / off loading of shipping
OR
Flight controllers directing lives on aircraft
OR
Surgery staff demand wages that will close EMERGENCY wards
OR
Police threaten to allow the mayhem of criminal activity
OR
John Setka's cement delivery union seeks to ruin construction safety, through non or slow delivery.
All are examples are of a PRICING that SEEK value of a duplicitous(?) dual value component. They seek to EXTORT, value that is not theirs to demand. I.e. a significant component that does not relate the endeavour of that WORKER. I.e. the value that that worker could attain in an industry that does not have a DUAL value. i.e. The labour value that is otherwise fully & freely priced.
This is fair... to society, employer and ultimately to the employee
