The subjectivist ... expects economic activity to be chaotic and unintelligible and he expects economic knowledge to consist of abstractions cut off from reality (for example, modern model building). In an unusually explicit statement of this viewpoint, Buchanan says "Subjective economics [is] a means of imposing an intellectual order on apparent chaos" (1982, 16).(3)

Modern economists take preferences as what they call "primitives" (Mandler 1999, 78). A primitive is a causal primary for which no explanation is required or can be offered. "We have to take human preferences as given" is the standard expression that sums up this viewpoint.(7) The consistent subjectivist view is that one's preference for a specific good or service is a simple, unanalyzable fact--an elemental starting point (Jevons 1871, pp. 45 and 65-66). Conceived in this way, preference has the fundamental characteristic of subjective value, that is, value as an emotion, and emotion as a phenomenon of consciousness independent of existence.

Why do people economize? ... Economizing is a means of protecting one's economic welfare, of defending one's standard of living, of preserving ones' business, and more generally, of preserving one's life. Economizing makes no sense unless there is an end at stake, and the only end consistent with the existence of an economy is man's life.

Most economic values are objective; they have an inextricable, positive connection to human survival. That connection is what motivates most of the actions of most of the participants in a free economy.

In opposition to the intrinsicists, the subjectivists hold that no facts of reality cause value. Nothing in reality requires a man to value a house more than an ashtray. Because no facts of reality cause value, whatever people happen to value is arbitrary, and therefore beyond rational analysis or investigation--a view that often is held explicitly. Again, Mises (1966, 95) made the clearest statement: "the ultimate ends of human action are not open to examination from any absolute standard. Ultimate ends are ultimately given, they are purely subjective ..."

Optional values are optional on the standard of the survival requirements of a rational being. Optional values are not required to live, but they do objectively support man's life. Indeed, mandatory values on the standard of man's life are unusual. They seem to be limited to medical treatments that are necessary to ameliorate a life-threatening disease or physical defect.

Nonobjective values are values based on something other than man's life (for example, unconsciousness, the environment, global warming, self-sacrifice, being green, the needs of others, God's will, nirvana, death), and/or values that orginate in something other than a rational grasp of the facts (for example, faith, hope, fear, self-hatred, fantasy, the opinion of others, arbitrary commitment).

Nonobjective values are not subjective in the philosophic sense. They are not phenomena of consciousness independent of existence. Even nonobjective values proceed from an evaluation by consciousness, of something, according to some standard. They are nonobjective because the evaluation is not based on reason and/or the standard is something other than man's life.

However, nonobjective values are subjective in the sense that the valuer does not know or care about the value's relation to reality.

The phenomenon of subjective value as proclaimed by the subjectivists does not exist. Nonobjective values are as close as men can come to pure subjectivity in their value choices. If subjective value means anything in reality, it means nonobjective value.

The modern concept of subjective value developed, in large part, as a reaction against and in answer to intrinsic value--a reaction that intrinsic value deserved. However, early advocates of subjective value had no concept of objective value, and therefore made no distinction between subjective value and objective value.

Not all economic values are objective. Some are nonobjective--they do not support human life and/or do not originate in a rational grasp of the facts, for example, charms, love potions, divining rods, religious articles--the things Menger called "imaginary goods" (1871, 53).

I also haven't read the book, but it seems from the quotes above that the author is to some extent conflating the concepts of methodological subjectivism (also known as 'methodological individualism' in Austrian parlance) and ethical subjectivism. 

Nonobjective values are not subjective in the philosophic sense. They are not phenomena of consciousness independent of existence. Even nonobjective values proceed from an evaluation by consciousness, of something, according to some standard.

From this perspective, Buechner's criticisms of subjectivist/marginalist economics appears off-base (though, again, I haven't read the book).  Thoughts?

It is valid for the farmer Menger imagines with two hundred bushels of wheat (1871, 129). It would be valid for other crops that are largely uniform, like corn and rice. ...

Nevertheless, this necessity of uniformity leads us to the one economic value in a money economy for which the law of utility is valid. That is money itself. Money is uniform.