In 2006, LEGO released 2 Vikings sets, all of these sets have been retired. For that year, the total price of all retail sets cost $70, today those sets are valued around $336, a growth of 379%.
Most valuable 2006 LEGO Vikings set
7021 Viking Double Catapult vs. the Armored Ofnir Dragon $169.13
Highest growth 2006 Vikings set
7020 Army of Vikings with Heavy Artillery Wagon +454.75%
2 sets

7020 Army of Vikings with Heavy Artillery Wagon

Theme Vikings
Year 2006
Pieces / Minifigs 312 / 7
Availability Retired
7020 LEGO Army of Vikings with Heavy Artillery Wagon
Retail $29.99
Value $166.37
Growth  +454.8%
Annual growth 6.9%

7021 Viking Double Catapult vs. the Armored Ofnir Dragon

Theme Vikings
Year 2006
Pieces / Minifigs 505 / 3
Availability Retired
7021 LEGO Viking Double Catapult vs. the Armored Ofnir Dragon
Retail $39.99
Value $169.13
Growth  +322.9%
Annual growth 5.5%