Given two same level equips, how much more does it cost to enhance an ‘orange’ equip than a ‘purple’ one?
You can check in tosbase.com how much cost each +, tos.neet.tv/ i think it also show but individualy (on tos.neet.tv), what i mean is, you have to do +1 at time, but be aware that i am not sure if it was changed at some point and if it was, they updated the values in the site.
I could be wrong but i think different qualities have different values.