hi, couple things involved, such as type of glass, size/type of over flow(s), and of course condition. starphire tanks being the more pricy option and often being custom built. i know this is a bad comparison being a new tank, but at the last lfs i visited it was $240 for a 90-gallon with one single centred over flow, and regular low-iron glass, no starphire. so for one in used but decent condition i would expect about $100+..? really hard to say, but i hope that helps somewhat
....also nice upgrade from a biocube!