If you are coming from the USA, oneworld has a European air pass with segments starting at (I think it's still) $75 each and going up to about $150 each. You need to buy two segments as a minimum. It includes some airlines not in oneworld, so you might be able to get BCN-ZRH-PRG.

The price won't be as cheap as EasyJet, but it might be more convenient. I've used them several times when the ORD-LHR fare has been low and I've wanted to do an open jaw to two destinations on the Continent.