The two on Robart are either $29.95 or $37.95. The $30 one is battery operated, while the $38 one is AC-powered.
I don\'t see an $8 advantage over being able to take up yet another valuable power strip plug, depending on what sort of batteries it takes and how often it eats them up. If it takes AAs, I\'ll be buying one since I have piles of rechargeables between my cordless mouse and digital camera. If it\'s something like a 9V, I\'m not so sure...if it lasts for 3 months on a single battery, OK, but not once a week or whatever.
Seems like a worthy investment to me!