I think you hit the nail on the head with the life-style change..Its not the boat market falling as much as its the economy going to crap and some boat owners are selling their toys to make ends meet.
You see it every year in those in the construction industry, as in the spring when the funds are comming in, there is a boom in 4x4 trucks and speed boats and in the fall, the same people are selling the toys to make ends meet as they're out of work and the cycle goes on the next year.
As for the swap between power and sail for a savings.. I figured it out a couple years ago as my brother has a large power boat compared to our 42 foot sail boat..
Every 10 to 15 years we can figure a new set of sails and standing rigging at 25 to 30 thousand dollars. and figureing fuel cost, thats 2 thousand dollars per year for the power boat for fuel and maintance.
You can buy a-lot of fuel and do a-lot of maintance for 2k per year..