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 $814, a growth of 394%.
Most valuable 2006 LEGO Trains 9V set
10173 Holiday Train $698.08
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 $58.00
Growth  +93.4%
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 $58.10
Growth  +29.1%
Annual growth 1.2%

10173 Holiday Train

Theme / Subtheme Trains / 9V
Year 2006
Pieces / Minifigs 965 / 7
Availability Retired
10173 LEGO Holiday Train
Retail $89.99
Value $698.08
Growth  +675.7%
Annual growth 5.5%