Red Flags for DMs?

[logic_error]

Sure... if you're playing an E6 game. If you expect them to go up against archfiends and great wyrms, though... don't blame me.

Also, magic abundacy depends on the genre and setting. If you're playing an Eberron campaign or a setting based on the Tippyverse, then magic should be dirt cheap(at least low-level magic). If you're running a game where people over level 3 are world-famous, on the other hand... you get the idea.

Eberron, despite being one of my favorite settings, is a bit funny. Merrix d'Cannith is a poor level 10 something guy. He can literally never come close to what you character would become in the game. This tells you something important about how seriously to take the game design there. As a DM there is a lot to balance in the game.

I think you can solve most problems in Eberron by treating most magic items as temporary charge based items or as infusions made specifically for you by your guild/ employer.

EDIT:

About going against Archfiends and Dragons.

I was never a big fan of that. It is always silly to have a dragon being defeated by players that are not close to Epic levels. This breaks my immersion seriously. A Dragon is supposed to be an *intelligent* ancient creature that can literally plot and plan its entire life. You should not be able to defeat it willy nilly. Don't even get me started on the Archfiends :P.