All of the windows you see in the size charts from the various companies are available at no particular premium for the different sizes other than the obvious fact that larger windows cost more and the larger they are, the less they cost per square inch of glass area.

For instance, the most expensive Andersen double-hung is their largest one but it is also the cheapest per square inch of glass area.

Andersen also sells their "cottage style" (smaller upper sash) windows at about 13% less than the equivalent regular style of the same size.

So, first you should determine the amount of glass you want, then the desirable head and sill heights, and then size the window widths in standard sizes to achieve that glass area with as few windows as possible, in reasonable proportions, and then consider making them cottage style.

Using Andersen as an example, a good value for a single bedroom window would be a cottage style double-hung with a rough opening of about 2-10 X 5-5 (WDH 2852C) because it has a very low cost per s.f., is large enough to be an emergency escape opening, and is a reasonable proportion for a cottage style with a muntin pattern of 6 over 1 (you pay for each muntin).

Here it that window 2 inches wider which might cost another $10 per window.

good to know- thanks for the info!