[cgriswald]

Assuming an advanced alien civilization can detect and interact with neutrinos in some way, neutrino communications could be very cost effective. They need only focus a beam from the flood of neutrinos coming from their parent star.

Lacking that, I can't imagine sending matter would be very cost effective relative to radio.

[marcosdumay]

Radio spreads. You can get a small chunk of matter very near c with a small part of the energy needed to send an easily detectable UV light bean to Alpha Centaury.