I don't know about other regions, but for Russia the prices are all over the place:

On GoG:
D:DC: ₽2009
D:DCIE upgrade: ₽509
D:DCIE: ₽2259 discounted down to ₽459

On Steam:
D:DC: ₽669 discounted down to ₽324
D:DCIE: ₽599

GOG put the Imperial Edition on sale; Steam went with the regular edition.

GOG:
DC:IE - US$8.99 (currently 80% off US$44.99)
DC - US$39.99
IE upgrade - US$9.99

Steam:
DC:IE - C$49.99
DC - C$10.99 (currently 75% off C$43.99)

Well then, looks like prices for other regions are fine. I'm mostly concerned about the 4x the difference between GoG and Steam.

It's one of the few games on GOG which is not regionally priced. On Steam it is...

There were some changes to Steam's recommended pricing recently, as well, based on fluctuations in the Ruble exchange rate.

Its now on sale at 80% off. I just got it.