Boat would be the only option for a rig as big as mine, and "really expensive" is a relative term. The cost of living full-time in a motorhome is highly variable and often has a very different shape than living a more stable life. When I'm doing very long trips, I probably spend more on gas in a month than most people spend on rent and food (I spent about $2000/month on gas during my Alaska trip, totalling about $5k for the whole journey). Spending $1000-$2000 for a ferry or ship to take my motorhome across wouldn't be what I would consider a show-stopping expense, and it's my understanding that that's the ballpark for this particular trip. It's just another thing to budget for. Moving, in a traditional fashion, to South America would probably cost even more, so from that perspective it's a bargain.