In regards to adding abilities I am confused as to whether improving a cloak of resistance +1 to a cloak of resistance +2 costs:
- 1.5 times the cost of a +1
- The difference between a +1 and a +2.
The language of the DMG reads:
A creator can add new magical abilities to a magic item with no restrictions. The cost to do this is the same as if the item was not magical. Thus, a +1 longsword can be made into a +2 vorpal longsword, with the cost to create it being equal to that of a +2 vorpal sword minus the cost of a +1 sword.
If the item is one that occupies a specific place on a character’s body the cost of adding any additional ability to that item increases by 50%. For example, if a character adds the power to confer invisibility to her ring of protection +2, the cost of adding this ability is the same as for creating a ring of invisibility multiplied by 1.5.
Obviously this item occupies a body slot but this isn't really a new ability it is improving on the ability the item already has.