HenryK,
Like most things involving boats, the answer to your question is....
It all depends!
It depends on, inter alia...
1. You...your knowledge, skills, intentions, licenses
2. Choice of Ham or Marine SSB equipment (or both)
3. Choice of new or used equipment
4. Your boat -- size, configuration, rigging
5. Who's gonna do the installation and testing? You? A professional? Both?
6. Choices you make for antenna(s)
7. Choices you make for an RF ground
etc.
The most popular marine SSB these days seems to be the Icom M-802. It's a very good radio, but it costs about $1,700 street price. Plus about $500 for an automatic antenna tuner. Plus over $800 to $1,100 if you want a Pactor III modem for HF email. Plus installation. Plus parts necessary for installation, including connecting cables, coax, RF chokes and insulators, s/s wire, ground strapping, etc. All that can easily run up to $5,000.
On the other hand, there are ways to go cheap. You can get a ham license, buy a used ham rig, learn how to use it with a manual tuner or make up some dipole antennas, etc. This would come in at less than $1000, maybe even less than $500 depending on your choices. Some time ago I posted on the SSCA Board info on how you might do this. This was also published in the SSCA Bulletin. See postings at:
SSCA Discussion Board :: View topic - SERIOUS HAM SSB SETUP ON THE CHEAP
Bottom line: it all depends :-)
Bill