Good suggestions, MAB.
I think the Enchanted Graduation Ring has a good value and it is fine where it is, but I think the other items are valued too high. By the time you are doing content that drops items of 6k or higher, I think those low level spell slots aren't as valuable as healer gets 6 spells per day of all of those suggested spell slots. They'd need some tweaks or just amount to loot table bloat since they're valued so high and offer little to the class. I don't think there's much danger in being a little liberal with spell slots healer gear since it is a support class.
My suggestions:
The Mender's Attire could be cheaper by dropping the AC modifier and the negative resistance, since at some point it'll be outclassed by crafted gear.
I might suggest the Cunning Folk Apron grant a 5-7th level spell slot, leaning towards a 5th.
The Blessed Lamordian Stethescope could grant a 4th level slot instead of the level 3, and maybe have some reduced saving throws vs. sound to compensate.
As you know values are not arbitrarily assigned. But I have no intention to add more penalties on those, nor to remove properties to lower these values. I'm not overly worried about their potential rarity. They will drop often enough anyway. Those will not be in the rare items treasury. I can assure you even low level characters venture in dungeons where 6k worth loot can drop, nor is it an obligation that they be found by them. The worse that can happen is that the higher level characters finding them will sell them back.
It's a non-issue for the apron for the reasons stated above, but also from the fact that even a level 2 characters may acquire high-end crafted items. The spell slots remain features no crafted armor can ever have.
Regardless of the precedent, I do not agree with the addition of items with bonus spell slots of level 5 or above. Spellcasters are eminently powerful by default, they do not need more spell slots of their higher tier spells on top of that. If another dev wants to create such an item so be it, they will get no opposition from me, but I won't be the one doing it.
It was my original intention to have the blessed sthetoscope to be a 4th level slot item, but that would push the value too far. Also, search as you will (and note that I'd be happy to be proven wrong for I've been searching for such exception for a long time) but you will not find any effect in the entirety of D&D 3.5 that calls for a saving throw vs Sonic. That is why arandur bonuses were changed to sonic DR in my last rebalance. But a 3rd level slot is nothing to scoff at either. i'm please with the result. I should probably add a line in the description that Lamordian physicians complain these blessed ones are less effective than the proper non magical ones (those are Listen +4).
