I'm not really an expert on windows but I do know you get what you pay for (sometimes less).
If you were to call my brother and ask him to install Anderson for you the labor quote will be higher than if you asked him to install Marvin or Pella, especially if they require jamb extensions. He'd also be charging by the hour rather than setting a fixed price.
I've got my father's barn stuffed with LePage windows waiting to go onto our frame once the stress skin is in place. They are solid wood (no finger joints) and the exterior has been stained prior to assembly so the wood is protected on surfaces you'll never see. The retail price on these windows was absolutely frightening, but the actual price paid wasn't, this seems to be common practice around here with the smaller window manufacturers.
The nice thing about dealing with LePage and companies like them is that custom sizes aren't a problem as they make up the units when ordered rather than pulling them out of a warehouse, this does mean a longer wait for delivery.
