From product standpoint - a helmet does last for some time. So its better to spend more and get a better product where one is secure. no guarantee how safe the shell is.
Still personally i feel something like helmet, buy a decent one to start with and be safe and have a good product that will stay in good condition after usage.
I just got a new GN helmet for our junior team. Here's a snippet of what is written in the instructions : -
Gray Nicolls reccomend replacing your helmet protector:
- after a severe impact from a cricket ball.
- after a hard knock or squashing it.
- after 2 years. Even with careful use, the performance of the product may diminish.
So even if you buy a 'quality' helmet, if you go by the book, you're up for a new helmet every 2 years maximum.
Everyone will have their own opinion on when to replace a 'perfectly good' helmet, so I can certainly see a spot in the market for a cheap helmet, particularly when the makers of the more expensive ones admit that they are not built to last.