"Objectively Desireable Ends"?

My comment on ChicagoBoyz:

It’s not in fact trivial to define “objectively desireable” ends. ‘Preserving the environment’ is not a complete description of an end. For example: one way to preserve the environment would be to release a virus that kills every human on earth. Hey presto, greenie heaven. So, to be complete, the cost must always be defined when stating a goal. Of course then we get into an argument as to how much we want to spend on ‘preserving the environment’. Thus it becomes a matter of subjective opinion again.
The key feature of the market is the way it generates prices. Prices give us an informed/rational basis for decisions about ‘preserving the environment’. That is they let us know how much a certain amount of ‘preserving of the environment’ is worth to us in terms of other things that we like.
On the other hand, politicians like to talk in terms of un-costed absolutes: they’re potential blank cheques signed by the taxpayer.
So at face value we are comparing a process where costs are unknown/irrelevant (politics) to a process where costs are known to a more or less exact degree. On its face which process is more likely to succeed in reaching a goal? (keeping in mind that a goal must be costed to be a real goal).