what difference does it make to have a "protected" cable (this is a direct translation from finnish, not sure if it's correct. finnish word is "suojattu.")
To my understanding "protected" just means layer(s) of shielding (copper braid/foil) wrapped around the cable. This would prevent noise from getting into the signal.
the store says protected cables show a better picture. what's this based on? why? how much better is it?
Not sure how "protected cables show a better picture" unless your display already had some noise/interference to start off with. It sounds more of a marketing term to me.
and can anything justify its price, which is about triple of the unprotected cables??
I believe most standard vga cables already have ferrite cores on them which serves the same purpose as shielded or "protected" cables.
Is it worth 3x the price for protected? I would say no. I have a standard 5ft regular vga cable (ferrite core at each end) bundled with two ac power cords and I have no interference/noise at all.
To be on the safe side you can buy both "unprotected" and "protected" cables and test them both and see if there is any difference and return the one you don't want.