The opposite extreme, of course, is unbridled power creep.
My goal is to make that number go down to (or below!) zero. Your goal is to prevent that happening.
Everything else is pretty much just gravy.
Situation: party has beaten its way through to a treasure vault, in which is a chest. On opening the chest:
DM:
You see six items in here: 1) a pair of dark-green boots; 2) a plain-looking gold ring; 3) a gleaming silver bar or rod about 2 feet long with no obvious markings; 4) a large and gently glowing orange gem; 5) a short length of silk rope, maybe 5 feet long; 6) a stoppered ceramic vial. All of these things look to be easily of high enough quality to be enchanted.
The DM's notes say the following about each item:
1) On donning boots, wearer and all worn or carried gear (incuding these boots!) instantly and permanently transforms into a large fir tree. Roots extend deep into the ground (regardless of ground material). Dexterity and movement speed become 0 and tree cannot become prone. Tree retains intelligence but cannot speak or otherwise physically communicate, though mental or psionic communication is possible. Chopping down or uprooting tree slays it; removing branches causes commensurate damage (etc. etc.)
2. On donning ring, wearer instantly gains a "hidden" wish: the next time the character speaks a sentence starting with the words "I wish" that wish will, as far as possible, come true. Once the wish is transferred (even if not yet used) the ring loses all enchantment and becomes a simple piece of jewelry worth 45 g.p.
3. Bearer gains best possible results when interacting, in a reasonable manner, with metallic Dragons. Has no effect or use otherwise.
4. On being touched to one's own forehead, gem immediately and permanently inserts itself there. Wearer gains at-will telepathic communication with any sentient creature that a) wearer has socially interacted with and b) is willing to receive such communication. If gem is removed from wearer's forehead by any means, wearer dies (no save).
5. While rope is being worn as a belt, wearer cannot be damaged by falling.
6. Vial contains a double-strength potion of healing; though all indications (smell, taste, etc.) point to it being a potion of giant strength.
Clearly here I either need some specific details as to exactly who does exactly what or there's going to potentially be some very big benefits and penalties getting tossed around by random DM fiat. So, details it is.