I don't doubt this thing is bright. But it's probably not built with quality electronics.
The cheapest I can find Cree Xb-d LEDs is $0.56 each in quantities of 1000 from a reputable distributor (Digikey), so that's $23.52 of LEDs alone for 42 LEDs.
Then you need a constant current driver or several if you want to get the rated amount of lumens from the thing. I built a circuit that drives six LEDs in series, stepping up the voltage from 12V to ~18V. I can't remember which chip I used, but it wasn't cheap as far as electronic chips go. It would certainly be a few dollars for each driver circuit, and you would need a few driver circuits.
So they are probably driving them directly from 12V. That means you'll get voltage fluctuations, so big fluctuations in brightness unless they have some regulation. But regulating more than 10A at 12V could be a bit tricky, so they probably don't even do that. So they have to design it not to burn up at the highest voltage it could see, maybe 14-15V. They probably have groups of 5 or 6 LEDs in series directly wired to input power. That's a terrible way to make a LED light.
If anyone has one, try leaving it on while you start the engine. I'm guessing the brightness will fluctuate a lot.
Then there's the heat dissipation. LEDs individually don't dissipate that much heat, but when you put a bunch of them close together they will get really hot, and they don't tolerate heat very well. As they get hotter, they tend to get dimmer, and eventually they will burn up. They are rated for 150C max, but at that temperature you only get about 80% of the rated output. The enclosure is aluminum, but without careful thermal design I doubt it would keep the LEDs cool enough. They would need to be on aluminum boards directly connected to the housing, and even then I think that much power might need some active cooling to keep the LEDs happy, or at least more surface area. It's probably fine most of the time, but in really hot weather it might get too hot. I doubt they do thermal testing.
I bet a significant number of the reviews are fake. Look at some of these:
Title: Five Stars
Very nice
Published 3 days ago by Mel Lindsa
Title: Five Stars
Well worth it
Published 3 days ago by Amazon Customer
Title: Five Stars
Fast shipping. Just as pictured.
Published 4 days ago by Raymond
Title: Nice light!
Great product and really good price. Very bright.
By Danielon November 11, 2015
These reviews add no value, and they hardly say anything about the product. They are all "Verified Purchase" reviews, but all that means is the seller had someone buy it, write a generic 5 star review and then they bought it back from that person. Or maybe there's an even easier way. The seller could make a fake Amazon account that they control. They could "buy" the product with the fake account, but not ship it to themself. As far asAmazon knows, a sale was made. Later they could use the fake account to write a review. If a real person is going to take the time to write a review, they will probably explain why they like it, or they probably won't take the time to review it at all.
Another tactic they might use, and I've seen it done for another product, is if you leave a bad review they will contact you and offer a refund and let you keep the product, or something like that, then ask you to change or remove your review since they helped you out. They know most people don't take the time to write reviews, but the ones that do have a lot of influence on their sales, so it's worth spending a lot to get rid of unfavorable reviews.
