Well it's your money so do what you want. 500K is a small amount of money though and honestly gil doesn't really have many uses in the endgame. It's good for some glamor, mounts, or buying HQ items for GC turn ins.

Housing if you are lucky. That's about it after that. Most any other uses for it get replaced with mats. Want to repair? There is a mat for that if you have the skill level on your crafters. Teleports? There is an item for that to do free or discounted teleports.

I guess of hard-core in raiding you can buy food/pots. Or make it yourself.