In the Gog catalog ?

Cheaper than D:OS is right now (on sale)? There's Temple of Elemental Evil. D:OS is pretty cheap at the moments so choices cheaper than that are limited.

You could maybe check out the Avernum series and other Spiderweb Software games. Of note:
* They're not quite as expensive, particularly the older ones. (And they sometimes go on sale.)
* There are substantial free demos of the games. (You can get the ones for the Avernum series from avernum.com )

Some RPGs that I could think of:

Divine Divinity (From Larian Studios too)
Arcanum: Of Steamworks and Magick Obscura
Eschalon: Book II
Torchlight II (On sale now)

Yeah, as Tremere said, it's hard for a lot to beat the current sale price of D:OS1. In fact, I'm pretty tempted to purchase it myself even though I want to stick to my budget plans. Decisions, decisions. :D

Never tried it, but i should mention this mod for this game, i remember to have played in the past (base game) and it's very punishing.

so i suggest to try with the following mod :

https://co8.org/community/index.php?threads/the-circle-of-eight-mod-pack-a-step-by-step-download-guide.1819/

be carefull , the gog version, may be already patched.,so extra patch may not be necessary (i don't have the time to read the whold thread)

Dragon age origins is currently on sale, cracking game.
Jade empire, ultima also.

I would second Divine Divinity, they are pretty cheap as well.

It depends on what aspects of D:OS you find appealing. Some aspects of the world design take cues from Ultima VII. However, if you're looking for turn-based tactical combat then U7 is a less plausible recommendation.

Nox - https://www.gog.com/game/nox

£0.99 right now

Nox is a different typeof game