The question then is how do we pay for the necessary professional development when we don't have the money to do so? One answer is look within - good professional development doesn't have to cost money. There are ways to utilize the resources in your own building or district and get quality professional development. All that's really required is a little time, effort and commitment.
Having been both a teacher, administrator, and now a provider of professional development, I have had a wide range of experiences with professional development and the many models that are out there. Each week I thought I would offer one suggestion for providing professional development on the cheap - looking within your school or district and using the resources you currently have to improve and support teacher change.
Let's start with defining professional development (from wikipedia ):
Professional Development - refers to skills and knowledge attained for both personal development and career advancement. Professional development encompasses all types of facilitated learning opportunities, ranging from college degrees to formal coursework, conferences and informal learning opportunities situated in practice. It has been described as intensive and collaborative, ideally incorporating an evaluative stage  There are a variety of approaches to professional development, including consultation, coaching, communities of practice, lesson study, mentoring, reflective supervision and technical assistanceI think teachers in particular lose sight of the fact that professional development is for personal development and growth, probably because so often the professional development they experience is mandated and irrelevant.
This weeks suggestion is something I have experienced myself and something I have seen personally be very successful. The suggestion is to provide designated planning time, where teachers who teach the same content (i.e Algebra teachers or 1st grade teachers) meet together and collaborate on new strategies or skills. It does require a commitment from administration to provide the time, and a commitment from the teachers involved to use that time constructively, but when it does happen, the differences in both teachers and student learning is powerful.
Collaboration on new strategies or skills can mean something like everyone deciding to use a cooperative group strategy to teach a specific lesson, or using a new technology tool as a warm-up, or trying out an exit pass at the end of a specific lesson. Everyone focuses on learning together about that strategy or tool in their time together, plans the lesson or warm-up or review...whatever the focus is, and then everyone tries it in their classroom and comes back and reflects on what happened. Maybe they look at student work, or discuss the problems that might have occurred and how to address those, or maybe it went really well for a few and they share the differences in what they might have done. The importance is everyone is focused on a similar change/strategy, they try it, share the results and then add to, improve, do a similar lesson or expand to something new. In my experience this works well if these content teams are meeting at least once a week together and trying one or two small changes within that week for discussion the next week.
Learning and practicing and reflecting together to improve instructional practice - slow and steady change. The collaboration and support from peers go a long way in helping teachers feel motivated and empowered to change practice. Creating this culture of collaboration is one way to provide professional development and growth and promote slow, consistent change and improvement in instructional practice. And all it costs is a little time and commitment.