In 2015, LEGO released 11 Seasonal sets across 6 subthemes, all of these sets have been retired. Subthemes for that year included Chinese New Year, Christmas, Easter, Halloween, Thanksgiving, and Valentines Day. For that year, the total price of all retail sets cost $68, today those sets are valued around $314, a growth of 362%.
Most valuable 2015 LEGO Seasonal set
40139 Gingerbread House $51.61
Highest growth 2015 Seasonal set
851358 Holiday Bauble White Bricks +284.98%
Theme / Subtheme Seasonal / Valentine's Day
Year 2015
Pieces / Minifigs 114 / 2
Availability Retired
40120 LEGO Valentine's Day Dinner
Retail $9.99
Value $18.01
Growth  +80.3%
Annual growth 4.4%
Theme / Subtheme Seasonal / Easter
Year 2015
Pieces / Minifigs 153 / 2
Availability Retired
40121 LEGO Painting Easter Eggs
Retail $9.99
Value $18.13
Growth  +81.5%
Annual growth 3.6%
Theme / Subtheme Seasonal / Halloween
Year 2015
Pieces / Minifigs 133 / 2
Availability Retired
40122 LEGO Trick or Treat Halloween Set
Retail $9.99
Value $30.24
Growth  +202.7%
Annual growth 9.3%
Theme / Subtheme Seasonal / Thanksgiving
Year 2015
Pieces / Minifigs 158 / 2
Availability Retired
40123 LEGO Thanksgiving Feast
Retail $9.99
Value $25.87
Growth  +159.0%
Annual growth 7.2%
Theme / Subtheme Seasonal / Christmas
Year 2015
Pieces / Minifigs 107 / 2
Availability Retired
40124 LEGO Christmas Winter Fun
Retail $9.99
Value $16.15
Growth  +61.7%
Annual growth 5.6%
Theme / Subtheme Seasonal / Christmas
Year 2015
Pieces / Minifigs 167 / 1
Availability Retired
40125 LEGO Christmas Santa's Visit
Retail $9.99
Value $29.74
Growth  +197.7%
Annual growth 6.2%
Theme / Subtheme Seasonal / Christmas
Year 2015
Pieces 233
Availability Retired
40138 LEGO Christmas Train
promotional
Value $35.49
Annual growth 5.1%
Theme / Subtheme Seasonal / Christmas
Year 2015
Pieces 277
Availability Retired
40139 LEGO Christmas Gingerbread House
promotional
Value $51.61
Annual growth 8.1%
Theme / Subtheme Seasonal / Chinese New Year
Year 2015
Pieces 99
Availability Retired
40148 LEGO Year of the Sheep
promotional
Value $44.53
Annual growth 9.4%
Theme / Subtheme Seasonal / Christmas
Year 2015
Pieces 62
Availability Retired
851358 LEGO Christmas Holiday Bauble White Bricks
Retail $7.99
Value $30.76
Growth  +285.0%
Annual growth 12.0%
Theme / Subtheme Seasonal / Christmas
Year 2015
Pieces 32
Availability Retired
5003083 LEGO Christmas Ornament
promotional
Value $13.23
Annual growth 6.1%