My simple equation on exercise using simple economics

I want to give a simple equation on exercise using simple economics.

In economics, if you want to sell a product. You can either price it high or low.
In a perfect world, if you price high, you'll get a small number of buyers. If you price lower, you get a higher number of buyers.

Revenue = price * quantity

So if you want an exclusive spa, price higher, a smaller number of customers. If you want an affordable spa, price lower, more customers. In a perfect world, you end up with the same revenue - this is my point of this equation.

In exercise, the similar equation that I invented is

Body exercise = quality * time

If you run, the quality is high, but you would run a shorter distance in less time.
If you speed walk, quality is lower, but you can walk for miles for a longer time.

In a perfect world, you would do the same level of exercise.