Yeah, everybody knows about SEOClerks. Well, maybe not everybody, but everybody who's in the IM business should know it.
While cheaper, a lot of sellers on there are kind of retarded, and that aside from them barely speaking English. Also a lot of services on there are total sh*t. But if you look hard enough, you can find gems.
Also, even if you do find gems, many of the sellers are unreliable. Or they'll deliver a good service and quick and everything once or twice, but after you buy a few times, it goes downhill from there. They get unresponsive, don't deliver correctly, don't deliver on time.
It's a hustle, as with everything. Though what can you expect with those prices.