The number of credits gained by is based on the rez cost of the ice at the time that his ability resolves, so the Runner can install a during approach with and to increase the number of credits he will gain on encounter.
Say I have Deep Red and am playing Nasir. Corp Rezes, I CMC a Rook, trigger to host on newly rezzed card. Does Nasir get +2 cash?
<a href="https://twitter.com/ChrisJFMartin">@ChrisJFMartin</a> Yeah that works. Rez cost is whatever the current value is.— Lukas Litzsinger (@RukasuFox) <a href="https://twitter.com/RukasuFox/status/495610029320318976">August 2, 2014</a>