In 2013, LEGO released 4 Friends Summer sets, all of these sets have been retired. For that year, the total price of all retail sets cost $87, today those sets are valued around $176, a growth of 202%.
Most valuable 2013 LEGO Friends Summer set
41015 Dolphin Cruiser $149.12
Theme / Subtheme Friends / Summer
Year 2013
Pieces / Mini-doll figures 33 / 1
Availability Retired
30108 LEGO Friends Picnic
promotional
Value $4.00
Annual growth 2.8%
Theme / Subtheme Friends / Summer
Year 2013
Pieces / Mini-doll figures 28 / 1
Availability Retired
41000 LEGO Friends Water Scooter Fun
Retail $6.99
Value $8.48
Growth  21.3%
Annual growth 2.7%
Theme / Subtheme Friends / Summer
Year 2013
Pieces / Mini-doll figures 94 / 1
Availability Retired
41010 LEGO Friends Olivia's Beach Buggy
Retail $9.99
Value $14.45
Growth  44.6%
Annual growth 2.6%
Theme / Subtheme Friends / Summer
Year 2013
Pieces / Mini-doll figures 612 / 3
Availability Retired
41015 LEGO Friends Dolphin Cruiser
Retail $69.99
Value $149.12
Growth  113.1%
Annual growth 9.4%