[Steam] Wunderling DX 90% off (1,24€)

this game is not sold on fanatical or HB

Since it was already bundled, it's easy to find it on grey market sites for less than $1.

Holds true only if you don't factor in payment fees inflicted on their customers. Cheapest offer I could find is EUR 1.46 (fees included) so Steam has the best offer atm besides being the better choice from an ethical POV.

no in the gray market it is 3 euros therefore more expensive than the steam offer

I was lucky to be able to get that bundle on a group buy, otherwise I would be tempted to buy the game at the current price, the game is nice and it's cheap enough if you'd really want it. But I agree with you, if you can wait, then it might be bundled again in the future, or it'll have a similar or better discount in a Steam sale event.

EDIT: As Mayanaise said below, the Indie Gala bundle was worth every penny just for Wunderling, the other games were sort of a "bonus" but the real gem there was this one.

I did all 6 worlds, not got all the secrets yet so can't comment on that, things are very fair, but can't say not tedious still finding some of those secrets (being behind hidden walls, so sometimes you keep wall hugging a level for a couple of times.
So can't wait what's in store with the treasure map after the end game.

https://dictionary.cambridge.org/dictionary/english/underrated
"better or more important than most people believe"
to me, 98% positive reviews means that most people believe it's great
so it's not "underrated" by definition...