I have checked the prices to SteamWorld series in GOG and Steam and it looks strange a bit: SteamWorld Dig 1, SteamWorld Heist and OSTs have equal price in GOG and Steam, but price for SteamWorld Dig 2 is 419 in Steam (without discount) and 699 in GOG. Are there any mistakes here?

I've had similar issue once and support said that they cant do anything, since not gog team set up prices, but developer itself (you can contact them, if you wish. But, since these devs didnt patch steamworld heist (other game in same universe) to be the same version as steam's for about year (if not more) - I doubt it will be helpfull).