Overall indication of damage Viking raids caused to Frankish kingdom.

For a summary of the damage the Viking raids inflicted in Frankia (roughly consider that as France or western Europe) from around 830 A.D. through around 890 A.D., consider the analysis by Neil Price in Children of Ash and Elm / A history of the Vikings.
He points out in about a century the Vikings went from perhaps a dozen men on the beach at Lindisfarne to thousands of Vikings on hundreds of ships besieging Paris for a year.
The starting caveat in his analysis is that we have to assume the comments in the various official chronicles are correct. A large assumption, but we can make no other.
How much silver did the Vikings take away?