First of all, you should know that there is no "standard" window price. Every situation is different and every contractor will set their own prices, so there isn't a standard price. Just like any product you purchase from a store, some places will have prices higher or lower than others.
Price shouldn't be your only concern though, you should also weigh the price against the quality of the vinyl window and the quality of the installer based on what information you can find. Replacing your windows is a serious task that can cause quite a lot of problems if it's not done correctly. It's not too difficult of a job to do, but it requires zero mistakes and knowledge of correct sizing, flashing, fastening, and insulating, to insure a draft free and moisture proof window. The prices of windows are typically relevant to the quality, which comes mostly true from the old adage "you get what you pay for".
Expensive is a relative term. What's expensive in your mind may be inexpensive to another, so the question "Are vinyl windows expensive" is really a question that can't be answered without further information.
There are quite a bit of links around this blog that you'll see will lead you to different brand pricing, which you may want to check out to find out more.
As a general rule, windows will cost approximately $200 to $300 for the vinyl window itself. The labor to install can greatly vary from $75 at the lowest and $300 or so at the highest. Then you have to add he company's markup and any additional charges like disposal of the old windows, permit fees, insurance additions, bonding, etc...
If you do your research, you'll often find that some companies can charge three or four times as much as others. In fact there are actually some window and siding companies that will charge 10x what others will cost! It really pays off for you as a homeowner (and the one that has to fork out the cash!) to learn all you can before you bite the bullet and order new vinyl replacement windows.
