A NEW digitizer / LED assembly will cost ~ $175. USD, in the US having PALCO fix it will cost ~ $200. ...
That being said, if you can get a cracked screen phone
(with nothing else wrong) cheaply enough, it
may be worthwhile to go this route.
However, if something else is wrong
(cracked screen usually means dropped phone), or Battery is
waning (new battery ~ $50.) that is not feasible. You roll the dice, when you buy non-working / cracked screen ...
I read something about Microsoft exchanging
busted phones for refurbs, allegedly for ~ $150. = $99 for insurance, $50 deduct for refurb phone ... don't know how true, might be worth checking out.
Check this
http://forums.windowscentral.com/nokia-lumia-1520/354933-lumia-1520-broken-screen.html