I think because it's very new and isn't widely distributed. If you go to TPTs classified section you can find it there pretty cheap (partly because it grows very quickly once established, especially emersed). I bought 2 big portions there a few months ago for $3 each plus shipping. It terms of its growth it requires more maintenance because it grows much faster but I imagine it's far less frustrating than HC (although never tried HC myself). Its growth is quite low. It's also far less demanding too in terms of substrate, co2, light, etc.