There is always more room to discuss (and I'm willing to take up follow-up questions from OP probably by tomorrow), but FAQ section of this subreddit, titled as 'Viking Loot and Viking Economics' has some answers to similar questions by /u/sagathain, /u/textandtrowel, /u/Steelcan909, and me: https://www.reddit.com/r/AskHistorians/wiki/darkages#wiki_the_norse_and_the_vikings