I can remember Keijo (scb ) saying in the past that Scandinavian stamps with clean socked-on-the-nose dated cancellations went for very high prices, so I'll guess a very high price - how about €30?
edit - I had a look at the Wikipedia page for Brumunddal and noticed it was in Ringsaker municipality, Hedmark county. I figured I'd have a look at a genealogy site I joined for the purposes of helping out a long-lost Estonian relative who is very involved with such stuff, and in a short trawl through the family tree, I found that I descend from Ringsaker people, going back at least to the 14th century. Gudbrand Tordsson Ingeberg, my 17th-great-grandfather!
I confess that I disabled the weekly e-mails I was receiving from that website, as I wasn't getting much use out of the updates I would receive. "Kersti Kaljulaid is Margus Lehtmets's ex-wife's mother's ex-husband's second cousin's wife's first cousin's ex-wife." Good to know!