This is certainly the major expense of a trip. You can of course sell the boat after the trip and recoup most of this expense. How much people spend on boats for doing a trip like this varies widely. I ran across them a number of times and they were having a great time with it.
Big boats can be fabulous with the right approach.
I did find out that very nice 30-40' boats are available in Ft. Lauderdale for a lot less than what they would cost in Toronto. My Contessa 26' was custom built with various options I wanted such as having the rudder modified for the self-steering gear and having all portlights openable. The standard Contessa is pretty well equipped for ocean sailing. She decided to use the same self-steering gear I had ordered, giving us a price break.