What to stock up on?

I bought quite a few hundreds of power crystal ores at 80k each , which is the most I'd pay for.
I would only earn if I get an advanced crystal from the appraising. (Having a hard time clearing out my basic crystals )
Black crystals aren't that much in demand as well , I've seen refined ones at
500k each and no one buying them . D:

Would you mind telling us how much refined diamonds (not enhanced by Maker, though) are worth now in MSEA? It'd be a big help. ^_^