It is VERY hard to describe, kinda like shrooms or LSD. You need to try it to understand it. Coke makes you 'sharper' 'faster' 'better' - it's like God mode. Of course, if the coke is crap, you'll only get jitters and racing heartbeats.
Coke is also an amazing appetite suppressor and fat blocker. I know people who use it to lose weight. I personally lost a good chunk in 5 weeks (good, as I was getting on the big side).
Price-wise, on no-clearnet (wink wink) the going price is about $200 for an 8ball (3.5) - for N/S America.