Opposing to Marx' theory, economists like Robinson more or less state that:
capital also contributes to creating surplus-value by making the means of production available...
Do they mean that the buyers of labor use profit to buy better machines -> produce more and consequently can be in the advantage of both?
I don't think they mean that.
It's an old argument which boils down to a very simple statement: without the means of production no labour can achieve anything, but the real twist is that these people assume that the means of production can only be "made available" in the form of capital, effectively meaning that labour cannot exist without capital. It is not a more or less scientific explanation of the whole process, but rather a sort of a moralist defense of the practice of exploitation. It doesn't explain how surplus value is produced, but merely justifies profit by assuming that no means of production could be put to use if it didn't appear in the form of capital.
In other words, this statement is obviously banal and tautological, but it hides some other aspects of capitalist apologism.
FKA LinksRadikal
“The possibility of securing for every member of society, by means of socialized production, an existence not only fully sufficient materially, and becoming day by day more full, but an existence guaranteeing to all the free development and exercise of their physical and mental faculties – this possibility is now for the first time here, but it is here.” Friedrich Engels
"The proletariat is its struggle; and its struggles have to this day not led it beyond class society, but deeper into it." Friends of the Classless Society
"Your life is survived by your deeds" - Steve von Till