You are making the false assumption that value is fixed for a fixed amount of work. Programmers, and more generally engineers, do not have a fixed value for lab

You are making the false assumption that value is fixed for a fixed amount of work. Programmers, and more generally engineers, do not have a fixed value for labor. It is generally the case that it is much more efficient to have the same engineer starting and finishing a project. This means that you as a programmer, have negotiating power that scales with the amount of work that you have already done. If you are not getting paid in proportion to what it would cost to replace you at any given point of the process, then you are getting paid well below the actual "market" rate. This means that if you are an at will programmer, you can do less work the closer the project gets to completion without it being a good idea to fire you. If a small raise disproportionately discourages this behavior, then it makes sense, but it does not count as "paying you more than the market rate". I suspect that you receive, on average, a smaller percentage of the cost of replacement as time goes on.