In 2018, LEGO released 3 Promotional Minifigure sets, all of these sets have been retired. For that year, the total price of all retail sets cost $7, today those sets are valued around $42, a growth of 499%.
Most valuable 2018 LEGO Promotional Minifigure set
5005233 Hamleys Royal Guard $19.12
Largest 2018 LEGO Promotional Minifigure set
5005251 Penguin Winter Hut 6 pieces
3 sets

5005233 Hamleys Royal Guard

Theme / Subtheme Promotional / Minifigure
Year 2018
Pieces / Minifigs 5 / 1
Availability Retired
5005233 LEGO Hamleys Royal Guard
Retail $6.99
Value $19.12
Growth  +173.5%
Annual growth 11.8%

5005250 Party Banana Juice Bar

Theme / Subtheme Promotional / Minifigure
Year 2018
Pieces / Minifigs 5 / 1
Availability Retired
5005250 LEGO Party Banana Juice Bar
promotional
Value $10.85
Annual growth 2.7%

5005251 Penguin Winter Hut

Theme / Subtheme Promotional / Minifigure
Year 2018
Pieces / Minifigs 6 / 1
Availability Retired
5005251 LEGO Penguin Winter Hut
promotional
Value $11.89
Annual growth 1.0%