Use value is altogether the bearer of exchange value but not its cause. If the same use value could be obtained without labour, it would have no exchange value.
Capital III, Differential Rent in General
The market for these commodities develops by way of the social divcision of labour; the seperation between the different productive labours transforms their respective products reciprocally into commodities, into equivilents for one another.
Capital III Introduction on ground Rent.
...the prices of things that have no value in and of themselves - either not being the product of labour, like land, or at least which cannot be reproduced by labour, such as antiques, works of art by certain masters, etc. - may be determined by quite fortuitous combinations of circumstances. For a thing to be sold, it simply has to be capable of being monopolized and alienated.
No producer considered in isolation produces a value or commodity...his product becomes a value and a commodity ,b> only in a specific social context
By a monopoly price here we mean any price determined simply by the desire and ability of the buyer to pay, indepentantly of the price of the product as determined by price of production and value. A vineyard bears a monopoly price if it produces a wine of exceptional quality but can be produced only in a relatively small quantity.
-Capital III, Rent of buildings, rent of mines, price of Land.
Useful quotes, I hope...