In 2018, LEGO released 3 Harry Potter Promotional sets, all of these sets have been retired. For that year, the total price of all retail sets cost $8, today those sets are valued around $100, a growth of 1148%.
Most valuable 2018 LEGO Harry Potter Promotional set
40289 Diagon Alley $47.17
Highest growth 2018 Harry Potter Promotional set
5005254 Harry Potter Minifigure Collection +346.93%
3 sets

40289 Diagon Alley

Theme / Subtheme Harry Potter / Promotional
Year 2018
Pieces / Minifigs 374 / 1
Availability Retired
40289 LEGO Harry Potter Diagon Alley
promotional
Value $47.17
Annual growth 8.8%

5005254 Harry Potter Minifigure Collection

Theme / Subtheme Harry Potter / Promotional
Year 2018
Pieces / Minifigs 25 / 4
Availability Retired
5005254 LEGO Harry Potter Minifigure Collection
Retail $7.99
Value $35.71
Growth  +346.9%
Annual growth 21.0%

6385434 Golden Snitch

Theme / Subtheme Harry Potter / Promotional
Year 2018
Pieces 35
Availability Retired
6385434 LEGO Harry Potter Golden Snitch
promotional
Value $16.81
Annual growth 5.3%