Is it possible that you have Obstructive Sleep Apnea (OSA)[0]? Being tired all the time and not being able to concentrate are prime indicators of sleep deprivation. I'm biased, as when I was in my late 20s, I was pretty much a walking zombie: tired all the time, unable to concentrate for long periods of time, cranky/irritable, etc. Then, while on vacation with family, my brother noticed that I was gasping for breath…
It is very likely that I have that. I don't think I have the money to purchase a machine for that.
I've continuously had health insurance over this time and I haven't paid (except deductibles and co-pays) a nickel for the four different CPAP machines I've had.
If you really do have OSA, not treating it because "I don't think I have the money" is a poster boy for "penny-wise and pound-foolish."
If I hadn't treated my OSA, I would never have been able to maintain my (relatively) highly-paid career and would most certainly not have been able to live a decent life.
Again, you may not have OSA, but if you do, I don't see how rejecting an effective treatment is a good economic choice.
If you had a brain tumor or a heart valve issue, would you reject treatment because it was too expensive? If the answer is "no," then why reject this (much less expensive) treatment?
If the answer is "yes," then good luck. You're gonna need it.
Edit: Fixed typo.