It can very so widely I wouldnt even venture a guess...
I bought a 125 from a member of this board
Tank, Stand, Canopy for $350, I got about another $200 in the filter...It can be done cheap you just have to look for the good deals..
razor, I thought I had an annoying avatar, you win....LOL...the flashing, my eyes, my eyes....LOL...
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Check the local newspaper for a used one, maybe couple of hundred (1-2) depends on the condition and brand of everthing. New no more than $300