I wonder if it has anything to do with areas trying to discourage using them, since they are so invasive in waterways?

I can imagine there is a short supply of water hyacinth early in the year after such a severe Winter.

So close to the North pole...

That is an outrageous price.

My four I think were $3 each last year. I ended up thinning them out of the pond at least 5 times over the season.

The garden center I go to had them, but I asked the guys and they both agreed I shouldn't get them yet unless I intended to bring them in if the temps drop

Good grief is right. That's highway robbery not to mention a few other disreputable adjectives which shall go unmentioned. Yet another reason it always pays to do one's research.