I am sick of "if you can't afford a cup of coffee" type of analogies. Subscriptions add up. Few dollars here, few dollars there, that is how they get you.If you can't afford the $3 or $7 dollars to upgrade to UHD, then maybe this a luxury you should bypass until you can.
If you are getting $16 worth of value watching Stranger Things in UHD, then more power to you. I think it's ridiculous that Netflix thinks it can raise subscription price every 18 months like a clockwork, and charging extra for UHD when none of their competitors do.