Budget 18650 batteries are usualy in the neighborhood of 2000mah give or take. Some are also reused rewrapped laptop batteries sold as new. This applies to ultrafire and trustfire branded batteries as well as some others. The 2 brands mentioned are the most likely to have false claims.
Currently there is no commercialy available 18650 that is over 3100mah. The true 3100mah 18650 cells are pricey compared to their counterparts with false claims. (3100mah last time I checked)
Cree is an LED manufacturer. Their LED's are installed in the most common budget flashlights you will see. Cree has datasheets available online for you to look at the real specs of the LED.
The majority of current budget lights are installed with a cree XML-t6. This LED is rated at 1000 lumens when properly driven. When you see a flashlight seller that advertises more than 1000 lumens with a single XML-t6 you are being lied to. Also note this amount of light will not make it out the front lens of the flashlight. Consider heat, driver, budget battery, poorly designed host for heatsinking, budget lens.
I hope this will help some people make an educated purchase on their next budget light. I like the budget lights but also believe you usualy get what you pay... not always.