In general, for the Chinese ones off eBay, the closer they claim to 3000mAh, the better. The 5000+ ones tend to be complete junk with actual capacities at or below 1Ah. It's like the worse it is the bigger they lie.

Of course, the hype has become standardized to some extent anyway, with giving capacities >1Ah in mAh. Might as well completely throw out common sense and require them to be labeled in kmAh.