The very essence of a "market value" is that it's not precise! I can sell you a barrel of oil at $75, but I might sell another to Jim at $65 five minutes later. Market value is not fixed, and is never fixed. It is in constant flux, and is entirely subjective.
Do you have any kind of a point to make other than this?
No... market value is not fixed but "fixed" does not mean the same thing as "precise." Fixed means it is set and doesn't fluctuate. Precise means it is accurate and exact. Many things can certainly be accurate and exact but not fixed... the time on your watch, for instance.
So you seem to be having trouble with comprehending basic language which is making communication with you very difficult.
A market value is never "precise." In order to be "accurate and exact" it would require it to be based entirely on tangible and objective metrics. However, as I have repeatedly stated, market value is subjective. Two jobs offering $40k a year may not have the same value. One might offer a series of bonuses in addition to base salary, while the other might offer no bonuses but pay on an hourly basis with the potential for overtime. One might have more favorable scheduling demands over the other. One might offer the opportunity to telecommute 90% of the time while the other might require 100% office attendance. One might be an advancement opportunity while the other might be an equivalent position as your current one.
These kind of intangible and subjective factors can factor in to a person's willingness to accept one or the other position. One company might be offering what amounts to a sweet deal for them, while the other might be offering what amounts to a very generous deal. The former might be completely unable to find another person who will accept the position for any less than $50k a year if I don't accept, with such alternates being less qualified or capable. My willingness to accept, or not, would be further influenced by my current position and circumstances. Maybe I'm so fed up with my current boss that I don't want to wait around much longer to hold out for more lucrative opportunities (or a more lucrative offer from the current companies).
You guys act like you're first year college students reading from a textbook. Maybe when you grow up and get some real world experience you'll realize that the nuances and details are far more intricate than the basic building block you learned about last week in lecture.