Actually The last time we got a price was two years ago and a 1810mm wide by 805mm high sliding window, with flyscreen, installed, came in at $2013.12.
Here are some DIY double glazing resources:
- the magnetic strip idea where I first saw it: https://www.instructables.com/DIY-Double-Glazing/ (although they say 2.5-3mm perspex, whereas the place I got ours said you want 4.5mm)
- way too much information about how to install plexiglass sheets in frames: https://plasticwarehouse.com.au/wp-content/uploads/2020/10/PLEXIGLAS-Sheet-Installation-Guide.pdf
- again, the magnetic option https://greenyflat.com.au/may-11-2018-diy-double-glazing/ with a link off to https://www.magnetite.com.au/ who will retrofit dobule glazing
- the magnetic tape i used, complete with a short video showing installation https://magnet.com.au/products/magnafix-12-5mm-x-1-6-mm-per-mtr-with-3m-adhesive-part-b
- An idea for custom making flyscreen frame + clear vinyl film glazing: https://renew.org.au/renew-magazine/diy/diy-insulating-aluminium-windows/
We did do the perspex and magnetic tape one of these on one of our aluminum doors, which was easy to do and cost about $300.