Using a NDG700 diode and a 1.8a driver from DTR, 12mm module and 8 dollar lens, then one of my 15 dollar MX-900 host with repurposed spring board and a 2 dollar length of 1.5 inch round aluminum bar stock drilled and tapped for set screws that I get 100 for 5 dollars or 5 cents each, and I bought 100 inch bundles of wire from Moghasam but you get enough from DTR to do the job if you buy a wired driver 27 dollars.
So about 220 ish is what I could build one for, but I do already own batteries and a charger, but for that 1.8a driver a cheap battery and charger would work.
NDG700 in module wired = 160
wired 1.8a driver = 27
3 ele for green = 8
mx-900 = 15
aluminum sink if you bought cut to 3 inches long = 5
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5 cents for a set screw brings it to 215.05
A cheap pair of 18650 and charger = 10 dollars
Between the wired diode and wired driver you have all you need.
You do need to own a 5 dollar drill and tap for 6/32 or 8/32 set screw that are dirt cheap and a 12mm drill for the module, a couple self tappers hold the sink in tight.
A cheap hand drill and vise from harbor freight 20 dollars
So even if you had to buy tools you could build it under 250
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Here's one ready made for 350 with profit for the builder.
http://www.ebay.com/itm/1W-to-1-4W-...032769?hash=item33b9b5d1c1:g:-SwAAOxyGxxSK7OM
p.s. I don't own a single surviving WL laser, their build quality is poor, heat sinking is piss poor. Some of their early pens were ok, I had a 55mw 532 that was an AAA eater but worked well for a while, but the krapton, I wouldn't want one for anything but junk parts prices.