Sash windows prices & Bifold windows prices are likely to be the highest. Next in line are tilting, with casement usually being the least costly. See a more accurate breakdown here: https://www.mylocalprices.co.uk/cost-guide/double-glazing-prices/
To protect the framework, you also must frequently repaint or re-varnish it with coatings that have anti-repellent mixture. And of course, keeping it clean would dissipate the termites.
How much do sash windows cost? – find out more here: https://www.upvcwindowsfitted.co.uk/double-glazing-cost/