Rough estimates based off eBay sold listings and my experience with selling them, in USD from US perspective.
Starbeam Twinkle: $15-20
Spring Fluttershy: $15-20
Diamond Rose: $35-45
Princess Luna Canterlot/Target Exclusive: $20-25
Lily blossom: $10-15
Sweetie Swirl: $20-30 (Maybe higher)
Trixie Lulamoon: $7-10
Shining Armor: $10-15
Princess Luna: $10-15
Dewdrop Dazzle: $10-15
Rainbow Flash: $30-80 depending on where you sell her
Snowcatcher: $15-20
Starswirl: $30-80 depending on where you sell her
Sunny Rays: $10-15
Applebloom: $10-15
Sweetie Swirl: Same
Blossomforth: $15-20
Daisy Dreams: $20-25, maybe more because forelock
Cheerilee: $10-15, more because forelock
Plumsweet: $25-30