There are some very cheap offers on eBay and some people find they work pretty well, but others find them shoddy or unreliable.
Although Cree emitters are very good and the XM-L T6 is a very bright spot, the only part of the lamp in the link that was made by Cree is the emitter. It is being sold as a Cree lamp, but everything else was made by God knows who and to God knows what standard. So you're talking about the reflector, the housing, the electrical connections, the controls, the waterproofing, the bar mounting, the quality of the batteries, the quality of the battery charger, and the general design, workmanship and reliability. All the things you're going to depend on are no-name.
The list of details seems to look ok, but check on Cree's website and they say the lumen output of a XM-L T6 is 1,040 lumens, so how does the eBay seller make out that his light outputs 1,800 lumens? By making it up. And if that isn't true, what else is? He doesn't even say what type of batteries they are, nor the burn time.
To be fair, even 1,040 lumens is very bright and it's going to be far brighter than an Exposure Joystick (£130 for 400 lumens). But how long will it last? Will it let you down suddenly? Will it fail in the rain? Will the batteries lose power after a few months? Is the charger a smart charger (certainly not) or do you need to keep an eye on it? If you look at the breakdown of the cost of higher quality lights, most of it is in the batteries and the charger, rather than the lamp itself.
I guess these things are so cheap though that you could maybe buy two and take the spare out with you every ride in case the first one fails.
Personally I would have more faith in this eBay seller, who has 100% positive feedback on over 9,000 sales and has done a lot of research if you check out his website. His price is higher than the cheapest, but a lot cheaper than the big names. He says there's a two year guarantee on this lamp, presumably through him, so maybe he is worth a try.http://www.ebay.co.uk/itm/300783148568
EXACTLY the same as
http://www.ebay.co.uk/itm/360477864104? ... 226wt_1398
Same charger, battery pack, headstrap, all he's done is get an orange wash, a bag couple of tatty boxes and a bit of foam for only 60 quid more
I don't think he's done a lot of reasearch just taken a few photos and spent 5 minutes on the net.
Edit, been using mine (9 quid) every day/night since I got it, never failed been out in the pissing rain for the last few day no problems. What people don't seem to realise most of the stuff coming out of China is made for named brands and as such the quality is really getting up there and those components are then used in unbranded/no name items.
The whole of the 'proudly made in the US of A' thing is a load of crap mostly they are chinese manufactured components ASSEMBLED in the US, this gives the company the right to say 'Made in the USA'.
I think too many people are waaaay overthinking this. All this talk of thermal runaway and but what if what if !!!!! Oh my god THERMAL RUNAWAY !!!!!!!!!!!
You're more likely to get knocked off your bike riding in traffic.