£484 | 360 | OSL-HEL-AGP-HEL-OSL | I-I-I-I
http://goo.gl/flights/Lp6q
I've deliberately picked the later flight on the RJ-190 to allow for a cheaper positioning flight on Norwegian for £80.
http://goo.gl/flights/xBNO
Total cost £564 for 360tp and no need for a hotel.