In 2003, LEGO released 4 Seasonal sets across 3 subthemes, all of these sets have been retired. Subthemes for that year included Christmas, Easter, and Thanksgiving. For that year, the total price of all retail sets cost $11, today those sets are valued around $38, a growth of 242%.
Most valuable 2003 LEGO Seasonal set
10090 Turkey $11.73
Highest growth 2003 Seasonal set
10080 Angel +331.33%
4 sets

10071 Mr. Bunny

Theme / Subtheme Seasonal / Easter
Year 2003
Pieces 25
Availability Retired
10071 LEGO Easter Mr. Bunny
Retail $2.49
Value $8.00
Growth  +221.3%
Annual growth 6.3%

10079 Snowman

Theme / Subtheme Seasonal / Christmas
Year 2003
Pieces 42
Availability Retired
10079 LEGO Christmas Snowman
Retail $2.49
Value $7.05
Growth  +183.1%
Annual growth 5.8%

10080 Angel

Theme / Subtheme Seasonal / Christmas
Year 2003
Pieces 33
Availability Retired
10080 LEGO Christmas Angel
Retail $2.49
Value $10.74
Growth  +331.3%
Annual growth 3.3%

10090 Turkey

Theme / Subtheme Seasonal / Thanksgiving
Year 2003
Pieces 54
Availability Retired
10090 LEGO Thanksgiving Turkey
Retail $3.49
Value $11.73
Growth  +236.1%
Annual growth 5.9%