Funny but yes when I was in junior high and high school, the kids from affluent families wore white Jockey briefs and the rest of us wore white Hanes, Sears, or JC Penneys briefs. I remember a friend of mine wearing Musingwear kangaroo pouch briefs during a sleepover and I thought that those must be really fancy underpants because I had never seen them before. There was very little difference in underwear then other than brands because almost everyone wore white briefs. Everyone wanted Levi jeans too but those were more expensive than the jeans from Penneys or Sears so if we had one pair of Levis we wore them every day that Mom didn't have them in the wash. That sort of brand awareness didn't happen when we were little kids but as teens we noticed it more which is why I can say that the boys from families with extra money wore Jockeys, Levis, and whatever else cost more.
When I got to college in the early 80s, there was more underwear variety in the dorms and lockerrooms but still 90 percent white briefs when I was a freshman and sophomore. I bought my first Jockey briefs during my sophomore or junior year. They were the low rise Young Guy jockey briefs in white and colors like blue, red, and yellow. I also bought some regular white Jockey briefs as those were considered better quality than the briefs that I had worn for years. I remember the Jockey prices were higher than the others. How much more expensive I don't remember but enough that I replaced my underwear over many months as I earned money in the summers and didn't splurge on trading it all out at once. I did the same thing with my jeans and shoes too. Went from the cheaper to the more popular brands in everything that I owned. I had some college girlfriends who bought underwear that they liked for me too. I still remember the one who gave me Jockey bikini briefs that were the smallest underwear that I ever wore other than jockstraps.
Moms did almost all of the clothes shopping for even teenagers in the 70s so most of them bought the least expensive underwear, socks, jeans and other clothing. That was very practical in my family as I had two brothers and there was a lot of handing down clothes from the oldest boy to the next to the next. We didn't hand down underpants officially from one brother to the next like we might do some jeans. Our Mom just washed everything white together and we picked our underpants out of a washed laundry pile on our bed which led to my brothers and I not being sure whose underpants were whose once we got to be close in sizes.