Just checked Wow airlines and it looks like they are having a nice set of prices for trips to Europe from the US. From San Francisco many flights in July in the low 200's one way, but not including luggage fees. Also, any quick return back to the US from Europe was much higher, but I think there were some pretty good back to the US prices in August. They will be an interesting airline to watch long term, as to whether they keep these low prices, or are they just introductory to build up name recognition and a market presence.
Checkout Norwegian Air Shuttle operating out of Las Vegas and Oakland in the west. We've flown'em to and from Europe twice since August on their brand new Boeing 787's with great pricing.
U.S. legacy airlines are raising cain about Norwegian's lesser paid Singapore based crews. We've flown Norwegian on 6 flight legs, and only seen substantial Asian flight attendants on one flight leg. The pilots were not Asian on any of the flights we were on. Price matters most to us, as they're hopefully going to be driving the industry to make some pricing changes.
I just did a sample SFO to Frankfurt roundtrip from early August to mid-September and it was possible to get a round trip ticket for 440$, but not including luggage. Amazing numbers.