We have a lot of slalom skiers in Ohio. There is at least 5 slalom lakes within an hour of me surprisingly and at least that many public lakes close by. We have 14 boats in our club. I did a quick mental count and 6 are 5-20K boats, 5 are 20-40k boats, and 3 are 50-100k boats.
The last 3 are Prostars. They ski a little better than my boat but I can't see replacing my boat with a MC that costs 5 times what I paid for my Malibu. If a new Prostar was 60k i could probably justify it but when things started approaching 100k it becomes out of my reach. I don't believe in payment unless absolutely necessary but I know I'm in the minority.
I also think that a new boater is not going to buy a ski boat when the surf barges are all they see at the boat shows.
I guess to answer your question, slalom is not dying but the prices are not helping the average person.