I'm not sure what caused the issue in your case but I can guess as it also happens with me sometimes when I'm not logged in but accessing the store with Russian language—the store might display USD prices converted to RUB from USD directly so the prices are way higher that their actual RUB prices when I'm logged in. Maybe it's due to VPN with Europe/America region? Please ensure you're not using VPN when accessing GOG.
I'm not Russia, but I can buy and activate Russian/CIS keys from Russian stores. GOG, however, suddenly decided that my country is twice as rich as Russia since they doubled the price. Right now on 50% off sale, Divinity 2 costs more than it was without a sale a few days ago in russian rubles. And these are correct prices, I'm always logged in and even with VPN prices are the same.