Many of the low wage earners your DH is 'subsidising' will be key workers providing services that are essential to your DH, even if he doesn't realises it, and this includes services not easily buyable no matter how wealthy.
And when you say "it's not fair", I may be a lowish earner (under the higher rate threshold), but I have personally saved someone's life, who was moments from death, in the last few weeks, my 12 hour shift yesterday finished 2 hours late (which is vastly better than 2 of my colleagues who finished 5 hours late at the weekend). So frankly it all depends on your definition of what is "fair". Why is your DHs time more valuable than mine? Is that just because historically that job has attracted a larger salary? Could that be because it is historically a male occupation? Or because you think he studied harder? Because I hate to break it to you but even poorly paid HCPs(band 5) are degree educated.
Your DH may think he's better than the zero hour contact minimum wage security guards, sub contracted by the NHS to keep the peace in A&E so that you, or your DH or your kids can safely received emergency care that you would struggle to access privately, but I disagree.