My first helmets were cheap end AGV plastic lids. They were comfortable only for short rides. They were heavy too. My current lid is well past retiring date, an Arai Vector. Twice the price to three times the price of it's predecessor. It is comfortable all day long. It is due for retiring only due to age. In terms of fit, comfort and finish it is as good as the day I bought it. If it weren't for the EPS liner aging I would have no reason to change. Cheper helmets tend to start falling to bits after a year or so. The Arai I can't fault in any area. I got it on sale for a good price too. If I can find something as comfortable I will be happy. I prefer full face over modular just because they're lighter, which my creaky neck appreciates.
First off, buy whatever helmet fits your head shape best (Unfortunately I have an Arai-shaped head so it's not cheap). Then pick the features that you want/need and then look at the price. You invariably get what you pay for and I can't fault the last few Arais I had. I bought an AGV as a first helmet, not knowing what I did later, and learned a lesson through buying cheap over a proper fit.
I got tired of looking for helmets when I got my license two years ago and when I found a helmet that my jaw fit into I bought it. AGV K3SV, probably not the best around but I just lost patience