From Oriental Adventures, p.141 (as far as I know it hasn't been updated to 3.5).

For comparison:

16 potions of CSW, heal 296HPs average, cost 12,000GP vs Mirror of Curing, heals 1100HPs plus status conditions, 11,800GP

You could get 10 scrolls of Heal for 16,500GP, but you need divine spellcaster levels or a high UMD score to use those reliably. Generally items which are usable by anybody, such as potions, cost double items like scrolls which require caster levels, so our default price for the Mirror of Curing would seem to be 33,000GP.

I know that often one big item is cheaper than lots of little ones, and also the Mirror has the disadvantage that it's, well, a mirror, and quite a large one at that, so it's not practical to use in combat and would probably require a type I Bag of Holding all of its own to carry it around without breaking it, but even so a nearly 2/3 reduction in the price seems quite generous.

What price seems fair to you?