Back in the day (maybe a decade or more ago), Lucis Art was unique among plug-ins, and had a price tag to match ($595). Since then, other developers' technology met and exceeded that of Lucis, which could not keep up and remained basically a one-trick pony.
It's always sad to see a business fail but this particular model (having to license the technology then outsource its development as a plug-in/standalone) was not sustainable in the current environment.