surely the CHEAPEST installation media would be one of those Micro SDHC cards (standard Micro SD adapters are available too). Up to 64GB available on one of those tiny things these days.
Of course the main problem here is that very few computers if any can boot from an internal USB reader (there's no fundamental reason why not but I suppose hardware manufacturers rarely update the BIOS these days).
If your computer recognises an external reader at boot time (in the boot menu) then the SD way to go would be my favourite --you could also store a backup image on it too.
Another good thing about a micro SDHC card is that you can also store it into a lot of phones so you wouldn't lose it when you needed it for restoring an image to your computer.
I do often store an image this way - now if the bootable restore program would recognise the phone as a USB device then that would be even simpler. Still Acronis at least recognises an external reader as an external drive.