Windowworld has three national buying contract's that I know of. Each of these vendor's provide a low medium and high grade of vinyl window to window world, the $189.00 price is of course the low end. Their premise is to provide the shopper with the lowest possible price on any type of window. I'm familiar with most of their marketing and as a whole they get the job done. I'm looking at some possible franchises myself. What I have found to be their weak point is getting qualified contractor's to get their work done. In area's where the local prevaling wages are higher then the national average they have a lot of trouble getting quality sub's.
What they do have is buying power and in general can provide the homeowner with the lowest possible price on a decent window.
For example an Alside Sheffield installed and wrapped for $349.00 is an outstanding bargain. You'd pay $450-$600.00 at other shop's. On the other side of the coin $189.00 for their std window is no bargain unless you don't care about the quality. They are well organized as most franchises are, and of course the quality and service varies from franchise to franchise. The important thing is to check out the local dealer their reputation and quality of installed product's.