Well it really depends on the quality of the product that you are intending on purchasing. Brand name? or Just a replacement?
If you just want a replacement i'm quite positive that you could find something around 400.00 tops. If i were you, i'd definitely measure up the door and go to home depot. I am very positive of the fact that they'd be able to better assist you with this matter and you shouln't have any trouble finding a replacemet.
I replaced my office door recently and i got a very good deal on it. I'm pretty sure you'd be able to find something decent for a fairly reasonable price.
Then again you really need to go and shop for the best deal. let me know how it goes.
Thanks
Urstupid123.