That'll only get you to 3m, added to your 2.5m only puts you at 5.5m.
You should be plenty safe unless you get another 200 of those and sell them.
It's roughly 5.5m on my server, so i'd be at 8m, not counting 1-2m in already-crafted stuff and 1-2m in stacks of gold\crawler\spruce\darksteel, both refined or not.
Ohwell, goldsellers are all about liquid gil, it's probably only about it. I'll make a point of staying under 3-4m.
(I bought Potash at 20k, and it spiked to 60.. i don't know if i should be happy or sad about this, considering i'd like even more of the damn thing)