Can someone explain why the game is cheaper on GOG than on Steam by as much as $15? Are these the same versions?

The price on both sites is still $80 CDN for me. They are the same versions.

gog 59.99$
Steam - 269 ILS = 74$
price difference = 14$

Might be a logistics issue with either website. That's more of a guess, I'm actually stumped. Sorry.

because Gog only has the plan edition where Steam wants to sell you deluxe [a guess]

Larian upgraded everyone to deluxe so it doesn't matter anyway

Ever since steam switched to local currency for israel, the prices have been higher compared to the US price and the price from other stores. Why that is - nobody knows, and steam doesn't seem to care.
These days I rarely buy games directly from steam because of that

the price is not set by distance so much as what they think they can get away with... for example Australians are used to paying more for items because of shipping and many devs [on Gog as well] like to take advanage of that