If there's a power difference to the point of coercion, it's coercion and one party is not consenting. Otherwise, it's still fair. Of course a company is "more powerful" than an individual. Still, a company cannot coerce you into working for them specifically.
As for informational asymmetry, that is part of trade. The time you spend on getting quotes is opportunity cost. It goes both ways, too. If you're selling labor, your employer has no way of knowing whether you're as competent or productive as you appear. There's nothing inherently unfair here.
Of course, there's a point at which informational asymmetry turns to outright fraud. Again, at that point there is no real consent.
> Contracts for labour are predominantly contracts which are negotiated in the context of power and informational asymmetries, which is why developed nations have backstopping legislation to prevent wholesale abuse.
Such as? Last I checked, nothing stops me from offering cheap junk for a ridiculous sum of money, nor is there a law preventing me from attempting to hire workers well below market rate.
There are some political attempts at price fixing (such as minimum wage), but they generally don't work. They're either so loose as to have practically no effect or they cause shortages/unemployment.