Looks like a fare war from California to southeastern Europe with Star Alliance and SkyTeam deals from San Francisco SFO, SJC and LAX to Athens ATH, Budapest BUD, Bucharest OTP and Sofia SOF with low fares from $454 to $531 round trip.
Low fare travel dates are departures Feb-April 2017.
Air France SFO – Paris CDG – Budapest BUD – Paris CDG – SFO
United Airlines San Jose SJC – Denver DEN – Munich MUC – Budapest BUD – Zurich ZRH – Chicago ORD – San Jose SJC
Momondo.com search TravelMerry.com online travel agency
Star Alliance San Jose SJC – Frankfurt FRA – Athens ATH (LH) – Munich MUC (Aegean) – Vancouver YVR (LH) – San Jose SJC (AC)
KLM Airlines Los Angeles LAX – Paris CDG – Athens ATH – New York JFK – Los Angeles LAX