Debatable. They used to be (a few years ago only) £30ish for a pair, now they are £50-£70 which shows they are much higher rated and very popular now.
I do like NB although that colour scheme wouldn't have been my choice.
If you're into trainers (which I am only a little, compared to my mate that has 100s of pairs) then NBs are not underrated. The general consumer however I think don't hold them in has high regard as they would more familiar brands like Nike, Adidas, etc.
Cheaper NBs I don't usually like, nor do most 'Trainer guys'. These are the cheapest pair I've ever bought and will be my almost daily pair until they're done. The 1300s above were £130 in the sale, that was in 2016ish.