Considering the number of boats, there really aren't that many for sale. Maybe 4-6 boats? Off the top of my head there are probably 80-90 active racing boats in the U.S. more if you count the guys that show up to one regatta a year.
The only boats for sale are used C2s and there seems to be little demand for them as the same guys have been trying to sell them for years... I can't find any used Nacra Infusions MKIIs and every one that has come for sale has sold quickly.
In the last year I've sold around 10 new Nacra Infusions. Considering the small market that's pretty good! The used ones have gone to people that are going to race them and they've gone for 15K+. I've got people begging me to find good used ones in the 13-16K ballpark. But used C2's for 10-12K aren't moving, I can tell you that Nacra has more recognition among recreational sailors, but I don't know why racing sailors are more dedicated to the Infusion than the C2. They are both competitive boats.
In California, Michigan, and Wisconsin the class is doing great.
The Northeast (which was the biggest fleet) has just as many boats as ever, we're just having a harder time getting them to regattas so we are building a central sailing venue in Newport, RI where about 12 teams have said they will keep their boats in the area to do weeknight racing.
This model can be proven in other areas where the class is doing well too, it's just much easier to roll down and go sailing and go home without having to trailer/rig/sail/de-rig/trailer.
I don't think Nationals are a great indication of how the class is doing. The class is made up of weekend warriors, asking them to travel cross country, take vacation time and serious racing is becoming harder and harder. Sure we took a dip the last few years in Nationals, but the fleets that are growing are not near where our Nationals venues have been.
Next year we are going to SoCal for Nationals, largely because the class is growing there. I am confident we will have 40-50 boats for this.
The next year we have F18 Worlds in Sarasota... I am confident we will have 100 boats for this. Like Long Beach in 2012 where we had 120!
The following year the Nationals will be in Michigan which collectively between CRAM and CRAW there are over 30 boats.
Australia is seeing it's biggest F18 Nationals ever this year.
2015 Worlds had 170 boats.
2016 Worlds in Argentina just didn't work out with getting boats there.
Overall the class is doing great. Anyone who says differently is clearly out of touch.
You can look at the interest in foiling boats, and the F18 class has talked about that. But I can tell you at this time foiling is not for the majority amateur sailing crowd. I have little to no interest in racing a highly competitive foiling catamaran and I've done my share of foiling and racing it in long distance.

Bach, I've heard you say the class is dead on numerous forums... you've been to maybe one nationals years ago? But I'm not even sure if you've been to one. And besides that have you sailed any F18 regattas? It's a shame that the Mid-Atlantic and Carolinas doesn't have an active class, but like all sailboats classes, there are going to be areas that we don't have racing. Of active sailors, I know there are 4 in NJ, 3 in Maryland, 1 in the Outerbanks, 1 in Virginia and a handful of others scattered about that I don't know about. If someone put together a really appealing regatta down there I'm sure we could get a decent fleet. I think you have a great spirit and following, rather than being negative about it, why don't you capitalize on the potential? I know the A Class has some scattered sailors through your region, but besides that not much else is successful either. Maybe getting all the boats together for more regional portsmouth regattas will pull boats out of the woodwork and the fleets people are interested in will survive.

-Todd Riccardi
USF18 President
Nacra North America