Star Alliance airlines have combined services for ticket prices under $400 round trip from Los Angeles LAX, San Francisco SFO and San Jose SJC to Scandinavian capitals of Copenhagen CPH, Oslo OSL and Stockholm ARN beginning late October and into January 2018. SkyTeam Alliance and Oneworld Alliance airlines are competitive too with tickets in low $400s.
Swiss Airlines San Francisco SFO – Zurich – Stockholm ARN – ZRH – SFO
$392.94 round trip Fri Nov 17 – Sun Nov 26 (Thanksgiving week)
British Airways San Jose SJC – London LHR – Stockholm ARN – London LHR – SFO
Air Canada San Francisco SFO – Toronto YYZ – Copenhagen CPH – Toronto YYZ – SFO
There are several other cities on sale too, especially in Norway with Bergen, Stavanger and other west coast cities.
Even lower ticket prices may be found through Momondo.com or Skyscanner.com.