The price also depends of where you are looking for one, where I am residing right now, South America, first of all if you can find one the price range is between $300 (for a ST, main unit only) upto $600 (for a STE, main unit only).
But look for one in Europe and you can find them dirt cheap, I got a 1040STFM and 1040STE for less than €50 (and both had a monitor included). I had to pay around €200 shipping cost but still a great deal .