I paid just over $300 at Petsmart. That was with the stand and the aquarium, but the aquarium had a setup package with a power filter and heater, and some little samples of food and dechlorinator. Might wanna check it out because buying the heater and filter separate can add up quickly. It did kinda suck too having to put the stand together, but I felt like I accomplished something afterwards at least.
It'll more than likely be cheaper to buy a used one, but I was a little wary because you don't how old the tank is and how the person has taken care of it over the years. At least with a new tank I know I'm the only person to touch it and it has a warranty in case it starts leaking or something.