Something for everyone to keep in mind, if Mattel were to take JLU to online sales/online only the cost is going to be considerably higher. Yes, it's a "budget line" because of the re-use of parts but online sales are going to mean smaller production runs and higher overhead than if these are going out to brick-n-morters. Honestly, I would expect a single to be around $10 if online sales happen.
Don't forget shipping. That's always a killer too.
That said online is the way to go if the line doesn't get picked up but only if they are sold directly by Mattel. Online toy stores often have AWFUL prices but if Mattel sold them directly that would be better for everyone. I like Bryan Long's idea about shipping being cheaper if they are shipped together too. I three pack of all new characters or of hard to find characters would be great too. They might as well go whole hog and release accessories too.
Conventions are ripe for scalper abuse on eBay. So I'm not crazy about that idea.
I think the line WILL be picked up though. JLU sells mad-crazy at my Target. LOTS of peg-warmers but those eventually sell too. Other than peg-warmers my Targets and Toys R Us usually only have a few figures on the shelves.