So this was, I'm fairly sure, an issue of contention early on. If we are basing renumeration off of provided labor, it would make no sense to renumerate a doctor and a janitor the same. Being a doctor is much, much harder. As with the idea of labor notes (which is by no means a unanimously favored idea among mutualists), what mutualists generally want to see happen is the labor of a task is a sort of form of labor in the market. So a market would necessarily emerge in which "doctor labor" and "janitorial labor" exist as different services in a market, and would reduce to a market based equilibrium of their relative value. The important part of this equilibrium which separates it from capitalism, is that this market for labor necessarily reduces only into labor. Mutualism doesn't seek to end the inequality of a doctor being valued more than a janitor, it seeks to end the inequality of both the doctor and the janitor sacrificing their labor product to the owners of the office being cleaned or the hospital the doctor works within (whether that labor product be extracted by capital holders, or state ownership).

As for the fruit example you brought up in the other comment, agriculture is somewhat hard. But if you can imagine "agricultural work" being reduced to a function of labor in a market (and a lack of extractive property claims over agricultural land), the monetary cost of buying the fruit itself will reduce to a fraction of the cost of the labor itself, so if renumeration is predicated upon strictly labor, the cost of goods will come from the cost of labor, rather than vice versa (as in capitalism) when for example, the cost of food and housing dictates the bargaining power of the laborer.