You can obviously buy more expensive milk to, which would give it price parity... But there are also more expensive replacement products. On average, the replacement products cost about 50-100% more.
The only way to save money via vegetarian meals is by making everything yourself and not the finished products from the supermarkets (at that point the relationship reverses - making meat meals about twice as expensive)
And I feel the urge to point out the obvious: the reason why the vegetarian replacement products get ever more space in supermarkets is precisely because they've got a gigantic profit margin, whereas the "traditional" milk/meat products have razor thin margins
Sure, but if nobody buys them, a 1000% profit margin won't get them very far. So I think that it's a good enough indicator that more people are buying these products.
First time I noticed them there, but mind I don't go to Aldi that often.