Yikes. I'll look in to a better battery for the sump pump and maybe a portable generator for the house. You are right though, the damage and time spent on the clean up may make it worth the investment.
A decent 5000+ watt portable will run $500 and up. A Honda, while very quiet in comparison to most can hit $1000.
Both the portable and the automatic backup Gens have their advantages and disadvantages. For something like what Sandy caused, the portable is most likely the better option. However, it won't be useable "during" the storm under most cases.
For those in the more remote places where outages are more common, the automatic backup would probably be better. Power will remain on no matter what. You pay extra for the lack of interruption.