Don't know why you're being downvoted: Google had immense bargaining power with Visa (and the others). It might be a stretch to say they aren't paying 2%, but it's unlikely they're paying 3-5% + $0.30 flat per transaction (typical fees for small merchants going through a merchant bank payment processor, PayPal, etc.)
I doubt they have any negotiating power. Negotiations are always based on leverage, and second-best option. They have none of those. What can they theaten? To not take Visa or Mastercard in the Play Store? That they'll only take checks my mail?
Interchange fees in Europe are capped to 1.15% online and 0.2% on payment terminals, and I'm sure Google, Amazon, and other big companies are able to negociate better fees