Surge in Kaladesh Invention prices?

I've been collecting a full set of Kaladesh Inventions via cardmarket since last august. I already had a handful of the very cheapest (<= 20 euro) ones. I had also been lucky enough to open a Mox Opal :)

Now that I decided to go for it I figured I'd start with the most expensive ones. The most expensive four cards were Sol Ring, Mana Vault, Lotus Petal, and Mana Crypt, and I got that pain behind me asap, buying one card a month. Next 'tier' was about 200 and then a whole slew of cards were 50-80.

I periodically checked prices on cardmarket and kept a list of "ballpark prices" for the remaining cards; prices seemed quite stable for most of the past year. Trinisphere for example was about 60-70 euro for most of that time, with plenty sellers available. It is now the last card I need, however in the last 2 months it spiked to 200+ euros, and there are only 6 sellers offering NM copies anymore on cardmarket.

Other cards (not all of them though) appear to have risen a similar factor in the same period O_O Did something happen? Is someone trying to corner the market?