Cost is 200 dollars on Gearbest with quasi permanent coupon code (check chinnature channel to get the coupons).
The idea of using 500w leds is not new and it is actually much more expensive , heavier and less safe/redundant:
It is more expensive because : you need to add, not only the basic LED cost, but a reflector which is crucial (a led without a reflector will not produce a beam of light that is usable at a certain distance or for a certain width), the cost of a led driver (that alone will cost dozens if not close to hundred dollars), a heatsink, a heatsink cooler (fans or water block cooling), a casing and the most of all BATTERIES!! Don't forget that for 200 dollars you get the DX80 with a LiIon 4S2P battery pack included (just the cost of such battery pack alone is more than 100 dollars).
It is heavier because : the efficiency of LEDs has diminishing returns with its size and power : for the same quantity ol produced lumens, you need more amps for one bigger LED cell than for multiple smaller leds. More amps for more powerful LEDs requires bigger batteries, bigger heatsinks, so more weight.
If you compare the lumens/gram ratio of the DX80 versus an array of 100w leds (you need an array of minimum three 100W leds to get the same lumen output as a DX80 flashlight), the DX80 is a clear winner : ratio of 32 versus ratio of 21 for an assembled LED solution (source : stratus aerial lights, who are producing and selling a solution as you propose)
It is less safe and redundant : when you have of one high power led failing you do not have anymore light...While on the DX80 you have 8 independent LEDs.
It has a much lower lifetime : CREE XHP70 high power leds have a 50.000 hours lifetime. You get reduced lifetime with higher power LEDs.
So using DX80 flashlight or even using multiple DX80 heads (you could discard the individual battery packs and use a bugger single one for mutliple heads) still seems to me to be the best solution.
For example you could achieve 100 000 lumens with three DX80 for a cost of 600 dollars, BATTERY included !!!