What is the difference between RPC and EPC?
In practice they measure the same thing: money earned divided by clicks. RPC, revenue per click, is the term search feeds use. EPC, earnings per click, comes from affiliate marketing and many trackers display it by default. The real question is which clicks are being counted, visitors or paid ad clicks, not which label is used.
EPC in a tracker is normally revenue divided by clicks received from the traffic source, so it behaves like RPV. Feed dashboards usually report RPC per paid ad click. Mixing the two leads to the classic beginner error of comparing a feed RPC of $0.90 with a traffic cost of $0.20 and assuming a huge margin.
Related figures you will meet: RPS, revenue per search or session, and RPM, revenue per thousand searches or page views. An RPM of $160 per thousand visits is the same as an RPV of $0.16. Pick one unit for the buying side and one for the selling side and keep them consistent.