Ring-a-ring of Regeneration

A campaign I am playing in at present has among the options for starting gear a weakened Ring of Regeneration, healing one HP/hour (I am unclear if it also does the restoration of lost bodily parts). This has led me to think critically about the SRD standard ring of regeneration and I have come to the conclusion that it is overpriced for what it does. Let's take a look....

Ring of Regeneration

This white gold ring continually allows a living wearer to heal 1 point of damage per level every hour rather than every day. (This ability cannot be aided by the Heal skill.) Nonlethal damage heals at a rate of 1 point of damage per level every 5 minutes. If the wearer loses a limb, an organ, or any other body part while wearing this ring, the ring regenerates it as the spell [within a round - M]. In either case, only damage taken while wearing the ring is regenerated.

Strong conjuration; CL 15th; Forge Ring, regenerate; Price 90,000 gp

I don't even know how they get that price and caster level, by my calculation it should be
7 (spell level) * 13 (minimum caster level) * 2000 = 182,000gp
or even
7 * 15 (given caster level) * 2000 = 210,000
Is it halved because of the "only while wearing the ring" limitation? Or because as discussed below the replacing limbs/organs never really comes into play?

( What else could we get for that money? )

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( A more realistic cost? )

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( How about a real Ring of Trollish Regeneration? )

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Finally (for this post) another quirk which seems to me to be a good candidate for adding to an ongoing healing item (perhaps one which was a prototype or not quite made right) is a slight loss in Constitution (2 points, to make sure the bonus drops). Is the healing going to be worth the ongoing fragility? That might very well depend on the wearer's normal maximum hit points and level.