It's not that much for someone that's been playing for a long time, but seems to be a lot compared to most everybody else. Maybe because I leveled off of leves and made my own stuff, I've currently got 10M+... and all of that was AFTER they nerfed the amount of gil awarded from leves and things. People that have played (and crafted) consistently since launch have significantly more, though.
We have a lot of level 50 people who somehow say they can barely afford to get their gear repaired, and... I'm just kind of baffled? Most of my gil came from selling crystals and crafting leve rewards, which everyone should have access to.
But, yes, 5.5M is good - the accessories from Aurum Vale and Cutter's Cry are some of the most expensive items now, and most are under 500k. The Mage's Choker is around a million, maybe? And there are some expensive materia, too... but those seem to top out around 500k for the very best ones.