He said it costs $50 (original Panasonic cells), but it's sold online for $100-120
It's impossible to get it for only 50$
Modern laptop batteries are made from multi Li-Ion cells and a controller chip, dead batteries doesn't mean all cells are dead, sometimes one cell or two cells or even the controller itself is the reason, and sometimes "believe it or not" many dead batteries aren't really dead, it only requires calibration cuz LiIon & LiPo cells wont accept a charge if they are not fully calibrated !
Well, what i want to say is that for 50$ definitely you'll get a refurbished or a re-calibrated battery, and your old one will be fixed and sold for another 50$..