I don't remember if this was the case back in Sep. 2020 when the game and all DLC were released here, but it's the case now for certain expansions. The highest base price in the U.S. for any single expansion is $4.99, whereas the GOG versions of several (The City and all the Digital Edition-exclusive expansions are examples) are $5.99. A lot of the other expansions are priced equally in both stores, and I think all of the smaller DLC are, as well.

Did the developers lower some of the prices on Steam at some point in the last year and a half? And if so, are they aware that they forgot to lower the prices accordingly here? Or maybe it's intentional, and this is just a weirdly inconsistent "DRM-free tax".

Whatever the case, my interest in buying more DLC for the game will be considerably lowered for as long as there exists a discrepancy. (Yes, it's only a $1.00 difference -- less when on sale -- but it's the principle.)

Edit before posting: If anyone's here's also active someplace the devs frequent (Steam forums or maybe a Discord), would you mind (politely) poking them about it?