With the Plugin directory a site owner can take it a long way. There are thousands of simple plugins available providing different functionality.
However I am coming across more Free + Premium plugins that give you introductory functionality and an upsell for more features.
I like this model. I was just checking out Booking Calendar WordPress Plugin. It has a Basic and Pro version. I don’t have any need for calendaring on my blog, but being in the events industry I see a lot of simple sites that could use this type of functionality.
I’m going to install the FREE just to play with and see what it offers.