Their standard socket bulb prices aren't bad (about $15 if you get a 6-pack), and they do produce bulbs for the slightly different European sockets, but shipping to Europe is about $40 (plus I'd then have to deal with picking them up at the customs office, which is always a multi-hour ordeal). But assuming I haven't found something decent before I'm next in the US in March, I'll pick some up then.

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.