It is highly psychologically addictive, but in it's own unique and peculiar way. This is due to the way it works in your brain and relatively short duration, which is highly dependent on the chosen route of administration, but usually no matter how much cocaine you've purchased it is all going to disappear quite rapidly. The quicker routes of administration: smoked crack cocaine and especially intravenous administration (shooting\mainlining) are quite damning.
Here are your routes (in order of directness): oral, sublingual, insufflation, vaporized (crack), IM and IV. Oral is the least direct route, while IV is obvious the most direct. Common insufflation lies roughly in the middle.
Your typical cocaine experience thru the more direct routes goes something like lift-off, peak (positive effects most prevalent), come-down\crash (negative effects most prevalent). The more direct the route of administration, the more cocaine actually reaches your brain (and faster), the more intense the 'positive' effects, the shorter the peak is, and likewise the more intense the 'negative' effects.
So if one were to take cocaine orally or sublingually, the cocaine is absorbed much more slowly. Not all of it will get to the brain. The stimulation and euphoria is less intense (few if any recreational user would do cocaine orally) and the crash is less intense to non-existent. When you snort your cocaine it is absorbed more quickly through your mucous membranes, at least 60% of it reaches your brain and you'll begin to feel it within several minutes. Peak subjective effects are attained in ten to 15 minutes. That last's up to half an hour or so before you begin to feel 'less great'. You'll snort another line, and maybe another, and tolerance to the subjective effects will build even over the course of those few hours. Once there is no longer much cocaine exerting those 'positive' effects on your brain (i.e. inhibition of dopamine re-uptake) you start to 'crash'. This is best described as a fairly shitty\hellish feeling in your brain: mild to moderate dysphoria or general emotional malaise, anxiety, irritability, and... craving for more cocaine. You go from feeling really great, to a bit shitty and your knee-jerk reaction is to blow another line. If you do this you will feel okay again, temporarily.
If one were to smoke crack cocaine, it reaches the brain in 30 seconds and peaks within a minute and a half. Effects are more intense, and consequently more short lived. Arguable more addictive as well, because one will be taking larger and larger hits of crack more and more frequently. After it's all gone, you'll be down on your hands and knees looking for any bit of rock you may have dropped on the floor. You'll likely end up trying to stuff bread crumbs or god knows what else into your crack stem\pipe.
And that brings us to the absolute worst way to use cocaine: intravenously. You could have purchased for yourself an ounce of cocaine, or more, but if your plan was to IV it you'll be sitting there doing just that until it is all gone or you've overdosed. A common practice is to prepare as many shots as you can in advance; or perhaps a few mega-shots that you really intended to inject into yourself slowly for an ever-lasting coke rush... but which you'll probably end up banging all at once, and end up freaking out because you feel like a freight train in a tunnel going at the speed of light yet still aren't quite sure that was such a good idea. Then you'll crash a minute later... freaking out because you couldn't possibly get enough cocaine into your veins quickly enough.
The crash symptoms are also complicated by the fact that street cocaine can have many other substances in it, besides cocaine; including minor amounts of meth or other amphetamines and caffeine. These things can contribute to a harsher crash and prolonged insomnia. You can remedy the situation with an opioid at lowest needed dose (Hydrocodone or Oxycodone) or better yet an anxiolytic or insomnia medication such as a benzodiazepine (Xanax would be best but Klonopin, Ativan or Valium will do), or another insomnia med like Ambien or Soma perhaps. The thing to TRY to remember no matter what is that the crash symptoms will subside, usually after an hour or so. But having come down meds does help and it's the best thing you could do for yourself.
I've used cocaine just about every possible way you can imagine, even well after I came to the conclusion that it was a disgusting drug. Years ago I wouldn't smoke crack or inject it unless I had some benzos, an opioid, or I was speed-balling with it. If you're going to try it, just insufflate (snort) it. Try to get some benzodiazepine and don't let the crash get to you too much, that's just what the cocaine profile is all about and it does subside rapidly. If you do feel crappy enough coming down it is likely to turn you off of indulging in the future, which is a good thing. Cocaine is just as anti-addicting as it is addicting.