In 2006, LEGO released 3 Trains 9V sets, all of these sets have been retired. For that year, the total price of all retail sets cost $165, today those sets are valued around $764, a growth of 363%.
Most valuable 2006 LEGO Trains 9V set
10173 Holiday Train $647.60
3 sets

2159 9V Train Track Starter Collection

Theme / Subtheme Trains / 9V
Year 2006
Pieces 24
Availability Retired
2159 LEGO 9V Train Track Starter Collection
Retail $29.99
Value $58.15
Growth  +93.9%
Annual growth 2.8%

4206 9V Train Switching Track Collection

Theme / Subtheme Trains / 9V
Year 2006
Pieces 27
Availability Retired
4206 LEGO 9V Train Switching Track Collection
Retail $44.99
Value $58.11
Growth  +29.2%
Annual growth 1.4%

10173 Holiday Train

Theme / Subtheme Trains / 9V
Year 2006
Pieces / Minifigs 965 / 7
Availability Retired
10173 LEGO Holiday Train
Retail $89.99
Value $647.60
Growth  +619.6%
Annual growth 5.4%