Apparently someone at Apple forgot to update all the localized pages for Logic Pro X. Let me clear it up for once and for all:
No matter which country your Apple ID is set to, the latest version of Logic Pro X (10.2.4) and the second-latest version (10.2.3) are only compatible with OS X Yosemite (10.10) and above. However, Logic Pro X 10.2.2 and below are compatible with OS X Mavericks (10.9) and above.
The differences between 10.2.2 (Mavericks-competible) and 10.2.4 (latest build) is minute, and there are no file format incompatibilities. If you are on Mavericks, you wouldn't be missing out too much.
With that said, you can not "purchase" Logic Pro X on a Mac running OS X Mavericks. You need to purchase it first on a Mac running OS X Yosemite or above, then go back to your Mac running OS X Mavericks, go to the "Purchased" tab and click "Download". Then, your Mac will prompt you to download the latest compatible version - which is 10.2.2 and is what you want.
If you don't have another Mac running OS X Yosemite or above at hand, navigate to /System/Library/CoreServices/ in Finder, then drag SystemVersion.plist to desktop. Open it in your favorite text editor and change both system versions from 10.9.5 to 10.10. Then save it and move it back to /System/Library/CoreServices/. You will be asked to authenticate. Type in your administrator password. Then go back to App Store and "Purchase" Logic Pro X. Once download begins, cancel and delete the download-in-progress and close Mac App Store. Then change the system version back to 10.9.5 in the plist and fire up Mac App Store again, go to the "Purchased" tab and click "Download". Then, your Mac will prompt you to download the latest compatible version - which is 10.2.2 and is what you want.