1stly:- You can farm gil from both dungeons (Alagan pieces) and leve quests.
2ndly:- Equip is converted to Materia, although end game gear doesn't have any materia slots which does make it slightly redundant and needs looking at.
3rdly:- There is profit to be made you just need to know what to make.
4thly:- I agree totally, having this kind of data would make a massive difference to selling and also provide a more stable marketplace where its easy to see for new players to see the average sale price of previous items instantly. (I've been asking for this since 1.0)

I can only hope that add ons will allow us to the 4th suggestion.

I would hate to see a taxing PvP style system in this game.