I would consider price compared to use. Here in Minnesota a client want to extend the season of use for their screened porch. It would have been about 5,000 for the least expensive windows. Instead we cut flat polycarbonate to fit each screened window with a compressable pin setup to remove and install them seasonally. They are able to heat the area effectivly as a 3 season. It would have made sense to install 5 grand in windows if the area was intended to be permanently integrated into the living area.
As a result to cost savings were over 4,000. There is little to no aesthetic difference. The air is allowed to fully pass through the screens in summer. There is greater security since poly is near indestructable to most burglars.
Hope that may be helpful. As a side note it wasn't a "let's be cheap solution". The porch had a 30K fireplace, iron and reclaimed barn wood throughout. It just seemed the senseable option.

Thanks so much for the great idea. We will certainly investigate this option since our goal is to use the space during the cooler months as well as summer.