It's one middle schooler's lunch, how much could it be, 10,000 yen?
Roughly $100 bucks, so yeah, is way too much money for a middle schooler lunch.
This series is pretty fun even if the premise falls apart if you think too hard about it, but well, nothing wrong with a self indulgent story every now and then. Reading 11/2 2.0 after the influx of Yuru Oyako's chapters is going to be weird.
Also, that is a fantastic twist. Shyamalayan would be proud.