Human welfare is not merely a function of income (broadly defined as you like), but also of one's past income, and of the incomes of others.
The hedonic treadmill and status competition are important characteristics that enable organisms to successfully compete. They also ensure that we will never be able to actually achieve the happiness we imagine. Being satisfied with what you have, in terms of income and social position, is a biological suicide proposition.
We may not be willing to step into the Experience Machine. But we must not fool ourselves into thinking that this is because there are real things in the world (intellectual or otherwise) that we value more than pleasure. It is because many of us lack introspective access to the fact that all we value is pleasure. We imagine there is a difference between real experience and pretend experience, between made-up stories and the "real" story of our lives we tell ourselves. To satisfy our need for a sense of meaningful existence, we must paradoxically imagine realness. Unfortunately, "realness" is often measured in terms of one's effect upon the experiences of others, or upon the material substrates of that experience, inside and outside human bodies. Experience, however, remains all there really is.
We are evolution's nightmare machines. And there are billions of us, imposing our nightmares on each other and on the rest of the natural world, in the service of imagined future happiness that will never come.
Luckily for our genes, and at great cost to ourselves, we have evolved self-deceptive biases so that we fail to realize this and don't kill ourselves.