You're right - those little Hondas rarely go on sale. Heck, even lightly used ones can sell for close to that sale price.
SailUSVI... just be very, VERY careful using these on a boat. They're not grounded into the electrical system the way a true, built-in machine would be. You also have to be very careful about CO poisoning. Some people do use portable genny's - but most are not aware of the very serious issues. Instead, they revert to the "I see others doing it so it must be OK" line of thinking. Wrong. Every year, there are also deaths associated with these around boats. I can list more specific stuff in regards to the safety aspects, if you want. But the main point here is that they are not an "easy" solution to onboard power.