Since no one really knows and the difference might be only £60 for a one time purchase why would you take a chance with the cheap helmet?
The Poc Trabec is costly but it is designed with additional reinforcement that means it can take more than one impact before it needs replacing. I’m not sure of how that is specifically designated but I had a small off in mine the other day and gave the back of my head a reasonable clank. The polystyrene is fine and there is a tiny indent in the plastic shell. I think in any other helmet I would feel the need to replace it.