Let me just add that there are other app stores you can buy apps from, e.g. the Amazon app store, if you have reasons for not using the Play Store.
If, as I hope is not the case, you meant "where can I download paid apps without paying?", please consider two things:
(1) if the app developers don't get paid for developing apps, why should they do it at all? The logical end-point of such piracy is that it's not worth anyone writing apps in the first place.
(2) if a site is willing to rip-off the app developer, where are they getting their money from, and why should they not be willing to scam the downloader as well? In fact the sites which offer free downloads of pirated apps are riddled with malware, and often insert it into the apps they have pirated. It's therefore a rather risky business dealing with these sites, and could cost a lot more than the couple of $/