| Well, how does it compare to a 4000gp Ring of Counterspells or an 18000gp minor Ring of Spell Storing?
Ring of Counterspells:
* Can hold up to lvl 6 spells
* Activates as an immediate action
* Only counters the specific spell stored in the ring
* Can't be used for a general Dispel Magic - only works for counterspelling
Ring of Spell Storing:
* Can hold up to 3rd level spells (or 9th level spells for 200,000gp)
* Activates as a standard action
* Can't be used for counterspelling (standard action to activate)
If you ignored the "standard action" clause on the Ring of Spell Storing, you could get pretty close to the mark by getting a greater one and putting Quickened Dispel Magic in it.
Alternately, just figure it as a Ring of Quickened Dispel Magic (handwaving the difference between swift and immediate actions -- they're all "free actions" anyway):
caster lvl 13
spell level 7
2000 / 5 = 400gp (base / usable once per day)
13*7*400 = 36,400gp
What exactly does the Ring of Spell-Battle do? Since I don't have the book it's in (MIC?), I can't compare it to anything. | 
And yet another word from our sponsors
