Manufacturer does not want that, because then it will lose most of it's distributors in Germany.
NB: Though I am not debating if it's right, fair or best for consumer. Just mentioning, what I've experienced.
If I know I can go online and it'll be some % cheaper, I'll wait and order it online, defer my gratification for a few days, and end up with a cheaper product.
Not sure about Poland, but most B&M brick and mortar stores in the US are distributors/resellers of the brand, they buy for $4 and sell for $10, and their rent/labor/etc costs $3 and they profit $3. Another distributor let's say is an e-commerce website, they can setup a warehouse in a rural area with cheap labor so it costs them $1 and they profit $5... so they can afford to discount it to $7 and make $2... which the B&M store can't do because they won't profit at all.
I remember hearing our marketing folks talking about enforcing MAP, at the company I used to work for. That company didn’t have the clout of Amazon, but we did sell premium kit.
For us, it wasn’t about money, as much as we didn’t want to ever be forced to reduce Quality; which included the shopping experience. We were concerned that outlets selling lower-priced kit, also had a worse shopping (and support) experience, which we believed (probably correctly) would reflect on us, and our most favored retailers.
Premium brands are often driven by factors other than just money. Brand reinforcement is a really big deal.
You're interested in Quality above all else, fine.
You're upset that you have competitors who don't care about Quality, fine.
So you make your website harder to use, so that... what?
I was just sharing my experience.
But it's not the manufacturers that do that. It's the cheap-slingers. It's their Web site that has the "click to reveal price" button.