What's a "reasonable" price for accessories?

Currently (on EU) ancient accessories with High-High are sitting at 2-2.5mil gold. You can probably catch a High-Mid for 600k, usually they are 650k. Judging by this sheet the KR average was ~1.5mil at the time, no idea how their market is looking rn. And obviously the actual damage gain from any accessory will depend on your class. Classes with high innate crit dmg won't gain as much from rings for example.

That said, at what point would you generally consider it worth buying a High-High over High-Mid. Current price, 1.5mil, 1mil, lower? I doubt it's gonna be gatekeeping criterium anytime soon, but at some point it's gonna become the next most gold efficient thing to upgrade.