he'll get somewhere between $200 - $500 each. being that they're props and may not even be seen the usage is low.
encourage your friend to look at the bigger picture if they offer him a low sum -- he'll get free exposure.
if your friend gets greedy they could cut using his stuff from the shoot. then he gets nada.
often, in commercials and print shoots, we have an artist create a custom piece that we don't need to worry about usage. problems come when people call in and ask where they can buy the stuff. that happens more often than you might imagine.