Diesel, on-highway in New England, is averaging $4.205/gal[1] (probably more in the city, especially more in a disaster situation). Applying your information to the above question and assuming they can get just shy of five gallons per bucket, it's probably a fair estimate that each bucket carries more than $20 of diesel fuel and accounts for seven minutes of generator time. So, about $3 per minute or 5.1 cents every second.
Really puts things in perspective.