I don't understand why you think the price of the computer has anything to do with any one specific function. I can't believe people pay thousands for a fancy Windows setup and the thing still gets viruses and crashes a lot! (also, the old saw "I paid 3K for this" is both a lie by about double, and undermines your credibility. Apple sells exactly one model of computer that costs three grand, and you don't have it).
In point of fact, there is a simple "show duplicate items" in iTunes that will quickly point out duplicates based on name -- but when I run that on mine, for example, it just shows the various alternate versions of the same song (remixes, live versions, that sort of thing) because I don't have very many duplicates.
Normally iTunes will let you know if you're trying to re-rip a song you've already ripped, I think ... but if you're just adding pirated music files, then of course the files are not named the same, the bitrate's different, etc so these aren't, in fact, "the same" files -- so they get duly added.
This could of course be avoided entirely by simply checking for one song in a given "discography" to see if its already there ... logic suggests that if it is, then the whole discography is likely there already. Doing a simple search on the artist name would probably also avoid the issue as well.
Or if that's too much work, here's a free script that will tell you if the tracks you're about to import from CD have already been imported: Doug's AppleScripts for iTunes - Ripped? v1.0
And of course, purchased tracks can be re-downloaded from the iTunes Store but you get a warning that you already have them in the library. But I don't know of anything for free that will help people who re-pirate music make sure they've only pirated it the once, sorry.