I ordered 3 xr-e from ebay for $2.7/pc (Offer Price) , and I was curious how perform these.
I did a quick measurment with a lightbox, the leds were attached to a big alu heatsink.
Take a look at the graph, these xr-e's are worth the money.
Y: relative brightness
X: current (A)
you can see how performs the stock xr-e Q5 from a small sun zy-c10 (green line), maybe it isn't a real Q5?
But the ebay leds are very good, really Q5 or R2 with a good overdrive capability.