Starting salaries are set based on what companies have to pay in order to hire the people they want. Exactly how they determine what's two offer each candidate depends on the company; they may have a standard rate they are currently paying for anybody in that initial position, or they may adjust it based on how much they want this individual.

These days, companies do not assume the employee is going to be with them for any significant percentage of a career, so unless this is an exceptional candidate their future value probably doesn't figure in that strongly.

Remember that value after training requires the cost of training, which has to be figured into the cost of bringing the new employee on board. And is that an employee started at a higher rate may find that raises come more slowly to compensate for that.

So, no, I don't think there is any principle here that you can use to argue for a raise at your current job. The best you can do is look at reports of typical/average starting salaries across the industry, without trying to guess what is driving those numbers, adjust based on relative cost of living, and try to guess what you might be worth on the market.

Or start interviewing and see how much you are offered. But see many past answers about the inadvisability of trying to use an offer to persuade your current employer to adjust your salary; they may take it as a sign that you are likely to leave soon whether they give you a raise or not.

Starting salaries are set based on what companies have to pay in order to hire the people they want. Exactly how they determine what to offer each candidate depends on the company; they may have a standard rate they are currently paying for anybody in that initial position, or they may adjust it based on how much they want this individual.

These days, companies do not assume the employee is going to be with them for any significant percentage of a career, so unless this is an exceptional candidate their future value probably doesn't figure in that strongly.

Remember that value after training requires the cost of training, which has to be figured into the cost of bringing the new employee on board. And that an employee started at a higher rate may find that raises come more slowly to compensate for that.

So, no, I don't think there is any principle here that you can use to argue for a raise at your current job. The best you can do is look at reports of typical/average starting salaries across the industry, without trying to guess what is driving those numbers, adjust based on relative cost of living, and try to guess what you might be worth on the market.

Or start interviewing and see how much you are offered. But see many past answers about the inadvisability of trying to use an offer to persuade your current employer to adjust your salary; they may take it as a sign that you are likely to leave soon whether they give you a raise or not.