Depends what you're getting. A basic lunch (which..... is nowhere near enough for a growing teenager lol) is typically only a few bucks, obviously depends on how much the cost of living is in general (a NYC student might spend more than the kid out in rural Corn Field Iowa, for example) but I can't say I've seen it go much higher than 5 dollars.

But again, kids rarely get just the basic meal if they can afford to, bc they'd go hungry otherwise. Schools typically sell things like chips, uncrustable pbjs, extra sides, etc to students too.

I grew up rather privileged, I never had to worry about lunch money, my mom just filled my account whenever she got notice it was low, so I don't recall exactly how much I'd spend on lunch, but I imagine it wasn't any more than 10 dollars at absolute worst. Even if we were very comfortable financially, my mom still woulda given me an earful if I blew more than that every day lol. Plus, I grew up in the Michelle Obama Era, and to those who don't know what that means, Michelle Obama's thing was making kids healthier by limiting junk food in schools. So even ad an "a la cart" thing, schools weren't allowed to sell overly sugary and unhealthy things lol (i started student teaching in the trump era, i was floored that the kids had soda in the vending machines lol. We were barely able to get gatorade to skate by). So there wasn't much worth buying in the first place.

Now all that said, it's been a very long time since I was a high schooler and I didn't pay attention to it that much when I did my brief stint in teaching in the late 2010s, so idk how much inflation has hit it now, but I wouldn't be shocked if kids were spending anywhere between 5-15 dollars on lunch, depending on how much extra spending money they got.