How is this legal for a seller?

On the first image we can see the price progression of the product in the last year and we can see it was set to 39.99 Euro for exactly one or two days in the whole year.

Then on the second picture we see the price now and the price which is reduced from, which is surprise surprise – 39.99 Euro.

So my question to Amazon is – how is this legal and why do they allow such bullshit???

First Picture

Second Picture

Link to the product