If you look at the comment from NortySpock in this there was a study to get a probe direct to Neptune and with a Falcon Heavy and extra kick stage it was "only"

If you look at the comment from NortySpock in this there was a study to get a probe direct to Neptune and with a Falcon Heavy and extra kick stage it was "only" 3800 kg. This is still an order of magnitude more than previous deep space probes (Voyager, New Horizons), but still not huge. It is still significantly smaller than something like our current geostationary communications satellites.