That's not a unanimous opinion. Over the years, there has been much discussion in print on that topic. Old timers say it was called uptown because it was up on a hill. Then it was downtown for many years becuase that's what the center of towns are generally called. Finally, uptown was revived by the Chamber of Commerce booster types as they wanted to project a more positive image.
As far as "cheaper is better" in Uptown, there are a few. There are a lot of higher end places that are pricey and a little more formal. Not formal per se, but not real casual either.
But here are a few places that are cheaper and pretty good:
Alexander Michaels - neighborhood bar in Fourth Ward. A great place to eat, drink, hang out.
Arpa - tapas - pretty good selection
Mert's Heart & Soul - soul food. Tasty and reasonable.
Simmons Fourth Ward - country cooking. Good value.
Presto - American food. Good choices and decent price.
Matt's Chicago Dog - dogs obviously. A chain place, but a good lunch spot for a dog.
There are a bunch of bars around for bar food and the like:
Ri-Ra (Irish); Fox & Hound; Graduate
There are probably more, but I don't eat out much in Uptown.