Find a random stranger and arrange transaction? That's as complicated as it sounds. The receiver loses money over paypal transactions and when withdrawing the money the money btw, it's very expensive from the seller's perspective which would have to raise the cost.
As someone who used to buy from G2A, if it's cheaper, I buy it. That's all there is to it. When you are broke, moral is less appealing, simple as that.
Ironically enough they don't have competitive pricing any more for a long time, possibly because they don't allow gray key sells anymore.
Anyway our country started having regional pricing so I just buy from first party nowadays.