UST Tyres are generally heavier – (there are LUST's (light UST's)), because they have a much thicker sidewall than normal tyres, so that when you run the low pressures you find it harder to rip the bollocks out of them.
However you don't have, rimstrip, tape, tube and other faff about things to add to the tyre.
As for a sub 500g tyre…. why do you want one?
UST means you get something that is virtually indestructable with stunning grip and rolling resistance, add 50ml of latex:water and you get improved resistance to punctures from thorns and the like (you don't get pinch flats). My UST's with some gloop slopped in lasted 14 months without me touching them.
I can understand trying to to UST on the cheap if you don't have UST rims/wheels, but otherwise? Needless pissing about.