Using www.skyscanner.com to find one-way flights for that set of cities results in a grand total cost of roughly $3800 per person. This comes with flexible dates and flexible routing since we'd only buy one set of tickets at a time.
I'm normally not a very spontaneous traveler: I like flights and accommodations booked ahead of time. However, it is seeming more and more likely that we are going to take off for a year of traveling with a pair of one-way tickets to get to Europe, a few nights of Oslo-Hostel, and absolutely nothing else planned.
Wahoo. I'm ready to go.