In the wage / rent / interest model, the skilled person's salary should probably be modelled as a mix of wage and rent.

The wage in its pure form is what a completely replaceable employee gets. The fact that the employee is completely replaceable will drive the wage down to the level where it barely covers the expenses to survive. Of course the expenses are different at different places, so the wages will reflect that, but that additional money just goes through you, and at the end you don't benefit from it.

The rent in its pure form is what you get for auctioning a use of a scarce resource (such as land). An intelligent person with mathematical skills good enough to work in IT is in some sense a scarce resource. They can be replaced (but you can also move from a piece of land to another piece of land), but it's difficult, and there are not enough skilled people for every employer's every whim. The employers are competing among themselves, and this creates the rent. -- If you could somehow separate your talent from your person, and send the talent to the work while you stay at home and have fun, that would be a rent in its pure form. But because it doesn't work this way, your wage and your rent are connected together.

And the interest in its pure form is money making another money. Which you can achieve by investing your rent in an index fund. So a techie can become an evil capitalist, too; it just doesn't happen automatically and requires some strategic thinking.