There are several threads that answer your questions, along with the tips in the guide forum

Here's the Plant Tycoon guide forum.

Tips on thought bubbles can help you determine why customers don't stay.

There's a thread that discusses customer "complaints" about prices here.

If you'd like to know more, you can use the Search feature up on the right hand side of the forums (If you aren't certain where to look, this thread has a screenshot to help you.)