This issue of purchasing and using a polarizing filter can many times be accomplished in the digital darkroom (e.g. Photoshop). In most instances in which a pro photographer would use a polarizing filter in a non-digital setup, I can replicate the effect quite reliably and nicely in Photoshop using curves and layers. The trick is to bracket your shots to get a range of exposures while still ensuring that you're getting good detail in the shadows. Ideally I'll work with an underexposed image and then duplicate its layer in Photoshop, setting the top layer to "screen" mode. Then by using curves and layer masks I can manipulate my images to achieve the same effect as a polarizing filter or a gradiated neutral density filter for enhancing the sky.
It's all a matter of intent. If you don't mind spending the time working with your images in Photoshop, you've got a wealth of opportunities at hand without the expense of additional equipment. Save your money for a warming filter instead.