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 $776, a growth of 471%.
Most valuable 2006 LEGO Trains 9V set
10173 Holiday Train $611.23
Theme / Subtheme Trains / 9V
Year 2006
Pieces 24
Availability Retired
2159 LEGO 9V Train Track Starter Collection
Retail $29.99
Value $72.18
Growth  140.7%
Annual growth 4.2%
Theme / Subtheme Trains / 9V
Year 2006
Pieces 27
Availability Retired
4206 LEGO 9V Train Switching Track Collection
Retail $44.99
Value $93.00
Growth  106.7%
Annual growth 4.2%
Theme / Subtheme Trains / 9V
Year 2006
Pieces / Minifigs 965 / 7
Availability Retired
10173 LEGO Holiday Train
Retail $89.99
Value $611.23
Growth  579.2%
Annual growth 12.4%