What am I implying? Just a question about how one can NOT already have iMovie. It's a real question because Apple installs it on EVERY mac they sell. Perhaps it was accidentally deleted? Perhaps this Mac is very old, from before iMove was available. Perhaps it is actually there in the Apps folder and the user does not know it is already there?
I really DO wonder why Apple sells iMovie and who would need to buy it.
Bottom line is you should never need to buy it.
Every mac has *some* version of iMovie bundled with it, that is true, there should be a version of iMovie on the machine somewhere unless it got deleted and there should be a recovery disk if it was deleted to put it back again.
iMovie 10 (the one which just got updated) was complicated. If you bought a mac since late october 2013, you got it bundled. If you owned iLife '11 either because you had it bundled with your machine (bought after late October 2010) or because you bought it from the store to upgrade an older iLife, you also got to upgrade it for free (via the App Store, but for free, you got a prompt to 'accept' some apps, that's how I got mine).
If however your mac was older than October 2010 and thus came bundled with an older iLife, like iLife '09 *and* you had never paid for an upgrade to iLife '11, then the upgrade to iMove 10 is *not* free and you have to buy it from the store.
I said it was complicated.
The poster who needs iMovie says they have a mid 2010 macbook pro, that should have come with iLife '09 and thus iMovie '09. That at least should be there. If the project he's doing requires the latest iMovie, iMovie 10, then yes that needs to be purchased. However I note also that the machine is running 10.7.5 which is too old for iMovie 10, you need 10.9 Mavericks for that, that's at least free.
... oh and I just found this link
http://support.apple.com/downloads/#imovie which has older versions of iMovie on it for download. I suspect if you bought a mac which had iLife '09 and lost iMovie '09, you can download it from there and re-install it.