Need to know what kind of window you speaking of. I am not familiar with the brands you mentioned. Also how many windows, wood or vinyl?
But the answer usually points to one thing. One contractor was less of a thief than the other. A resonable price for top quality windows is anywhere from $250 to $300 a window. Bow and Atrium windows or large windows are more of course. Tell the clown with $21000 price tag to take a leap. There are no windows on this planet that are worth that much cash...unless you have 1000 windows in your mansion.
Andersen windows are always my choice but, sometimes because of the openings vinyl windows are your best choice.