In 1998, LEGO released 2 Trains 9V sets, all of these sets have been retired. For that year, the total price of all retail sets cost $66, today those sets are valued around $532, a growth of 706%.
Most valuable 1998 LEGO Trains 9V set
3225 Classic Train $486.66
2 sets

2585 Track Buggy with Station Master and Cool Kid

Theme / Subtheme Trains / 9V
Year 1998
Pieces / Minifigs 32 / 2
Availability Retired
2585 LEGO Trains Track Buggy with Station Master and Cool Kid
promotional
Value $44.99
Annual growth 6.2%

3225 Classic Train

Theme / Subtheme Trains / 9V
Year 1998
Pieces / Minifigs 281 / 3
Availability Retired
3225 LEGO Classic Train
Retail $66.00
Value $486.66
Growth  +637.4%
Annual growth 7.7%