Here are the spices in order from least rare to most rare (I think): red, yellow, blue, green, pink, purple.
I can find buyers paying up to 70K per unit for my purple spice. I never let it go for less than 60K.
I've found up to 16K per unit for red spice. I don't let that go for less than 10K.
Everything else is in between. Yellow can get 22K; blue I don't remember, don't sell much of that; green & pink up to 50K.
Finding buyers are tough, yeah. I hold a lot of spice while flying around doing other things. I always open up the trade screen to check prices. This helps the tediousness of spice trading.
I have about 70 mil right now, and I've bought over 20 planet busters (5 mil to 2.5 mil each) for special delivery to the Grox.
In other words: Ignore red, yellow, and possibly blue.
Search out systems with green, pink, and purple. Be patient. They're around. I have one system with three green spice planets maxed out. I pull 80 spice from this system. I also have a purple spice and a pink spice in the same area.
Also, keep an eye on what other goods are selling for. When I see a good deal of something I use often, like colonies or planet busters, I always snap it up, even if what I'm doing at the moment has nothing to do with that item. That way I don't have to go searching for them when I need them.
