It should be easy enough to check the price of vlam glazing units. Although I am not familiar with pricing for IGUs four panes for $1200 doesn't sound excessive for a custom made product that will save you money and give you comfort until you die. My view is that the sooner you spend the money on IGUs, the sooner you reap the benefits. Prices for doubling glazing and energy for heating/cooling are only ever going to go up, and once you retire disposable income is only ever going to go down. Give yourself the greatest chance of ROI by starting sooner rather than later IMHO.
Oh, and don't even think about aluminium window frames unless you have polar bear DNA.