You could try a site like cjs-keys, they sell steam/origin keys cheap because they get them from eastern europe.
Its totally legal too.
Is that site really legal? I'd really love to buy keys from there if it were actually legal.
I wouldn't trust any site offering cheap Steam keys. All the prices take into account currency conversion (99% cases adding to the cost). On top of that the "super cheap" legit keys are generally locked to a locale so won't work on EU or US accounts.