I've done a sesh with coke once and it was a gram split with another person. I thought it was a great experience, but way overpriced of course since we're in the sticks. Lucky I didn't pay. I was talking about coke purity with a friend of mine who used to sell the other day and he said that the average can even be as low as 30%. He was convinced that everyone who receives what you could consider basically "off the boat" will cut it off the bat by a third. So that's 66%. And then as BluesHues said, plenty of dealers higher up won't hesitate to half something to improve their return. That brings us pretty close to the 30% number my friend said for the stuff you're getting from small timers. That is, if some other idiot didn't try to cut the product too.
I think it's probably 60-70% for the good stuff that people call fire, brah. And considering that, I think it's totally believable that in a lot of situations it would be as low as in the 30s.
You can be a chemist and turn impure into pure of course, and you can be that one guy in a million who actually knows or works for the lord and gets uncut. For me, because of this, I just never found coke worth it, even in a city.
Provided fire, brah, free of charge, I think it'd take it any time.
edit: does someone smarter than me know how pure coke can get? does it go up to 100%? it probably does and i'm just an idiot.