[PowerfulWizard]

Thanks, that's interesting -- I'll have to buy one of their bulbs to compare to my other LED bulbs.

Looks like the lowest cost might be the 100W COB LED ... It would need a bunch of supporting equipment but it might be possible to do it for around $2 per watt.

Edit: I guess the normal bulbs and the led tubes could also come in around $2/watt and they can take mains power so that might be an easier but physically larger route.