I go by /~Owls values, but generally prefer doing item-for-item trades (especially for higher-value items), but if there's something I really want, I may offer GBCs/custom :)
I also have sale sections for GBCs at the very end of this list, meaning some items are 2 items = 1 GBC/4 items = 1 GBC (or item equivalent), as well as a FREE section (no limit per person, except if I don't have enough gift boxes).
Styling Studio Supplies x2
Trendsetter Mystery Capsule II x2
Faerie Quest Fortune Cookie x5
May Fever Premium Mini Capsule x3
Styling Studio Prismatic Brush x3
Lab Ray Fortune Cookie x1
Training Fortune Cookie x1
Peaches and Dreams Premium Mini Mystery Capsule x1
Dyeworks Hue Brew Potion x5
2 items for 1 Gift Box Capsule
4 items for 1 GBC
FREE! No limit (besides # of gift boxes I have)
Not actively looking for these at the moment, but if the opportunity arises... :)