Obviously, I'm biased and I don't believe that I have ever been on a Seawind, but I did a quick search and Lagoon has built over 2,000 catamarans and they are one of the most popular catamaran
in the worldwide charter
fleet. Yacht World has approximately 350 listed for sale for $110K to $2.6M. That is probably about 15% of the quantity built.
Seawind appears to have produced around 500 catamarans. YachtWorld has 33 of them listed for $2,200 up to $634K.
There are a lot of Lagoon catamarans that come out of the charter fleet when they are 5 years old.
Personally, I wouldn't have purchased a Seawind at half the price I paid for our Lagoon 450. Not because there is anything wrong with it. It is just a completely different boat than what we wanted. Asking why the Seawind catamarans are nearly twice the price of the Lagoon catamarans would be similar to asking why do Lagoon has sold for times the number of catamarans than Seawind has, or why do Lagoon catamarans have nearly twice the interior
space of the Seawind catamarans.
You have probably seen this answer on Cruisers Forum before: Go to the boat shows and dealers and look at the boats based on how you plan on using it and what you can afford to buy, operate and maintain. Narrow down your choices after setting foot on the ones that might meet your objectives try to find a charter company, or even better a friend with those ones and get out and spend time on them doing the same type of activity that you would want to do if you owned it.
That's what we did and it was a good feeling to go to the Annapolis
boat shows and look at all of the catamarans there and agree that we still have the one that meets the most of our priorities for less than half the price of the one which would be our 2nd choice (also a Lagoon). To each their own. Enjoy the hunt, and then enjoy using it even more.
And for Sand Crab: I tried to like Mercedes but the total cost of ownership
is too high for what you get. However, I have never been disappointed by the Fords that we've owned.