Looking for good and cheap 3D game on GOG.

I love 3D games
Something like:
NWN1&2
RIME
Shadwen
Skylar &Plux
Ghost of a Tale
Kingdom Come Deliverance
Hellblade Senua's Sacrifice


Genre is irrelevant, and try to keep price low

I like the Darksiders series, which is currently on sale (but only the first two fits any reasonable definition of cheap).
Alan Wake is also quite cheap currently (but get the original one and not American Nightmare).
Depending on your budget (and whether they are one sale) these may be relevant:
» TRI: Of Friendship and Madness is a nice first-person puzzler.
» Octodad, which is a short game (~2 hrs or so) but quite amusing.

They're old, but I had plenty fun with Rayman 2 and Rayman 3.

Knights of the Old Republic is a classic.

I really liked Enclave a lot.

Painkiller Black Edition is great fun.

Have a look at Psychonauts is currently under promotion.
I have it and I think it's a good 3D game.

TRI: Of friendship and madness

one of the few games really making good use of all 3 dimensions

Doom.

Seems like a bit of a weird requirement if it's only about the technical aspect and even games like NWN 1 & 2 fit the category (as opposed to e.g. 3D platformers, open world ARPGs or similar). But okay. If I'm not mistaken, all the games you list are third person perspective, not first? Is that a requirement, too? If you're looking for TP 3D games under 10 EUR, how about:

- VTM: Bloodlines (75% off at the moment, best and cheapest suggestion right now apart from Psychonauts, but you've probably played both?)
- Red Faction Guerrilla Re-Mars-tered (50% off at the moment)
- Enclave
- Risen
- Total Overdose: A Gunslinger's Tale in Mexico

EDIT:
oh, and:
- Oddworld: Stranger's Wrath
- Beyond Good & Evil

Everspace is great, has awesome 3D graphics and can run on most machines.

It is worth every single cent, but wait for a sale if you prefer.

The same could be said about Phantom Doctrine. It is on sale now but it's not inexpensive.

Darksiders games would be your best choice right now.

SOMA is 5€ on GOG until the 5th november, and it is truly one of the best games I played these last 5 years, at least.

Saboteur - playing it right now, GTA in WW2!

Mafia 2 - though not open world, its a great story/game.

Gothic I, II and III.

Risen 1, 2, and maybe 3.

Gun

Gothic 1, definitely 2 and maybe 3. :)

I pick Serious Sam First Encounter.