not with bike gear. You buy cheap and if it's a shite helmet you might never buy again.
Honestly, there are certain things you shouldn't buy from aldi or lidl and one is safety gear. My dad got some kevlar safety gloves from Aldi. I decided to test them. They were meant for sawing.
I shot at them and they just embedded themselves in the polystyrene I put behind them. I lightly attacked it with a well used and not sharpened bread knife and it went straight through with no effort.
For food Aldi and Lidl are fine, especially if you enjoy the delicate taste of horse. For safety equipment I'd not buy anything that's not a big name unless it has been put through proper lab testing by a magazine. Even then I'm sceptical so I like my kit to be well tested.
I'd rather spend £200 on a pair of gloves and have just adequate protection than feel good having thought I've got a bargain at £20 and find they split open, destroying my hands on the road and my ability to work. Armour is easy to put in to kit and it's easy to say it's 1000D material. What's hard and takes time and money is seams and you can't test these in a shop. Even Knox screwed up the seams on recent gloves and they know better.
What often happens is that the company promises one thing and the factory decides to do something else and pocket the difference - see Frank Thomas's Titanium range where the titanium armour rusted because they were scammed by the factory in China.
The reason you pay extra isn't just for the brand, it's because the brand needs a reputation and therefore will take kit off the line and test it to destruction to ensure it's good. If it were me, I'd not do that - I'd take it off the shop shelves and test it.