Ring of enlarge person?

[Ridley's Cohort]

If the ring also forced an action to turn on each battle 1800 does not sound that bad.

Once you get up to middling levels, Actions are the main balancing factor.

Your typical non-spellcaster has 2-5 good buffs on hand. The spellcasters have much more. My mid-level Paladin has ~6 good options at his fingertips -- spells, scrolls, wands.

IME, if your DM keeps you on your toes, you can only get 0-2 short term buffs up before the blood start spilling. A cheap Ring of Enlarge Person will last 10 rounds. Does that really make your Top 2 list? Not for my Paladin.

The only real problem with a Ring of Enlarge Person for 5 times per day at 1800 gp is that in campaigns that are heavily slanted towards fighting humanoids, I can see how Trip and Grapple could get way out of hand. I do not think Dragons and most other monsters will care.