At $19/pop, why bother? I seriously think you should 100x that. If you aren't familiar already, search around for patio11's thoughts on charging for software (search term: "charge more")
I want to cater for "random blogs" ($10~$100), maths or physics blogs/websites ($100~$1000) and other usecases like teaching startups ($1000-custom) so for that I started at $19. The thing I'm unsure about is how to slice those tiers properly, if all I have to bargain is the license.
You can easily double the price. I'd limit the amount of support/feature requests that includes so heavy users will have to pay more :D