I'm a big fan of the fact that you can push a Brompton while folded. A feature that other folders miss.
There's no doubt that your bike is higher quality than the Decathlon one, but the average customer doesn't appreciate how well engineered it is or how many patents (??) are involved.
Folding bikes are complex and hard to make safely, and the folding mechanism is costly to engineer right. This means that the manufacturer of a cheap bike is either providing you with a dangerous folding mechanism, or is putting a lot of the cost of the bike into the folding mechanism, so there's not much money left for the rest of the parts. Either way, it means that cheap folding bikes are a bad choice, and the btwin folder is a good example of that.
As to patents: yes, there are patents.