An absurd luxury is something either super indulgent (possibly to the level of impractical) or something seemingly commonplace that you otherwise personally value immensly in your life and have taken note of.
The problem with the relevancy you indicate, is everybody has a different standard. Quite frankly most people on Lemmy have very privileged lives compared to the mean life on the planet.
yeah the absurd part is not having water. having water isn't an absurd luxury. if this is the kind of standard we're going by I might as well say "having opposable thumbs" since a vast majority of animals don't have them