The most obvious is you could control wages by being the owner of inelastic goods your workers require to live, such as housing. I think this is how the feudal system worked originally, workers produced cereals but the Land and the worker's cottages were both owned by the Landlord. If the price of bread decreased the Landlord could simply increase rents. So it was only when the factories came along that most workers managed to have any savings.
Another example is where a worker in debt, and must work at an existing job to pay for the debt. Obviously a worker without debt is a worker than could request a higher pay rate because they are able to be more competitive by obtaining a new employer.
Another example is the existence of non-compete agreements.
It should not surprise us that in London there exists widespread use of non-competes and their workers are typically indebted by student loans or mortgages, that the wages are so low. Look at any London software engineer thread if you'd like to be depressed, 300-400 a day and sometimes much less, for people with 10+ years of experience.
Another example is that I suspect that there is a conspiracy to hold down wages that involves both the government and companies price fixing. I further suspect this is a deliberate policy by at least the US and UK governments using a list of occupations they depend on to function. Scientists, engineers, programmers.
This shouldn't come as a surprise because even in Silicon Valley where the wages are the highest in the world for computer programmers, it was found that multiple well known corporations were involved in a wage fixing cartel. That however I suspect is merely amateur hour in comparison to the government and its partners.