I'm not sure the LF boys will go that low but it's worth a try. Didn't they only promise that price if you "buy today?" How many calls to the manager did it take to get the price that low?
I consider heat mirror a TP window. The only difference is it uses mylar between the panes instead of glass. The idea is that the performance of the krypton gas improves dramatically when you contain it to a 1/4 inch space.
My point is you can purchase a pretty good double pane window for around $550 or less in this area. Heck, the Okna 500 comes in with a U-factor of .25 in a double pane. That gives you an immediate savings of $4000 as opposed to purchasing the Quantum. At a savings of $125. or less
per year, it would take at least 32 years just to break even given the difference between it and a good double pane. I think it makes much more sense to spend the difference on new energy efficient doors and more attic insulation than to spend it all on windows. But that's just my opinion.
Have you considered getting an Energy Audit done before buying windows? Might be worth getting an unbiased opinion. An energy audit can help you pin point the areas of your home that would benefit the most from your attention to them. Don't assume windows will be a panacea to lower energy costs.