Long comment but please bear with me:

To me, it doesn’t make sense to say that money is non-linear or non-constant. Money is not a function of time, therefore it does not make sense to describe it with time-dependent terms such as “linear” or "constant”. Inflation, the change in the purchasing power of money over time, yes. Money, no.

Money is simply a token that we use to represent the intangible concept of value. I think your comment seeks to address a change in what individuals, and by extension and on aggregate, societies, fundamentally value over time.

I’ll return to that in a bit. First let me address the problem with your example: It ignores the compounding returns to performing similar actions over time. Economically: Human capital accumulation. Colloquially: Experience.

When you get your first entry-level salaried job, you are actually a liability to the company. You come in with a low level of human capital - the company is basically paying to train you, all the while putting up with any potential mistakes due to your lack of experience. Why would a company do this?

By hiring you, the company is making an investment in your stock of human capital. It takes on some risk up front in return for some amount of reward in the future when you are wiser. As you gain experience over time, (ideally) you perform increasingly valuable tasks with a higher efficiency. You have accumulated the one thing youth (or old age for that matter) cannot buy for itself: time.

Getting paid for 3 hours for "little to no work" is a drop in the bucket compared to 10 years of solid, salaried employment.

By comparison, one-off jobs which might net you $20 in a couple of hours are a completely different situation where a low level of human capital is not purchased by means of a salaried contract. Rather, it is rented with a much shorter time horizon in mind, generally for menial tasks that require little to no experience.

To connect this idea back to the larger debate of “lowering the value of work”: I think you need to specify what kind of work you are talking about. I agree that the value of human menial labor is constantly decreasing. Why?

The supply of physical, menial tasks (washing dishes or mopping floors) is determined by the inflows of the human birthrate (more humans=more eating=more dishes to wash) and the outflows of automation (dishwashing machines), among other factors. Automation adds value by adding hours to our lives that would otherwise be spent washing dishes. For menial tasks it is generally more cost efficient. Thus the outflow outweighs the inflow (decreasing birthrate) leading to a lower supply of menial labor.

I don’t think we will revert to a hunter-gatherer bartering society in the future. Markets and specialization are much more efficient forms of raising standards of living, which I define as the ultimate goal of “human progress”. I think we will eventually need to reexamine our definition of “standards of living” as we move away from the realm of the physical to that of the virtual. Perhaps one (sad) day food will be unnecessary, as we redesign our bodies to subsist on a different form of energy, or do away with physical bodies altogether. This standard of living does not take into account food, shelter, transportation, etc. – the fundamentals that we strive to improve today through progress.

Anyways, enough with the science fiction and philosophizing. The fundamental lesson here is that the market gets what the market wants. There are a lot of human beings, so menial labor, both physical and mental, is in high supply driving down its relative value/price. Technology is eating jobs from the bottom up. Increase your human capital so that your brain is more valuable than a charged hunk of steel. Be the person who knows how to operate the machine and you will never have to beg for a $20 bus ticket.