I think polarised sunglasses are a great way to experiment with polarisation effects, especially for beginners. For anything like quality work, though, remember that the best sunglasses have abysmal optical quality compared to even a half-decent camera lens.
Polarisers do many, many things that can't be simulated easily in Photoshop - or at all, in some cases.
Polarisers don't uniformly increase contrast in an image; they darken only polarised light. This includes light from a clear sky that's at 90 degrees from the sun; reflections off water, glass and most other NON-metallic surfaces. They don't alter colour. Simulating these effects accurately in Photoshop is very time-consuming indeed; tweaking layers and curves isn't the same thing at all.
A polariser can also serve as a handy ND2 filter to give you that extra long exposure or that shallower depth of field. Try simulating vehicle light trails in Photoshop; sure, you can do it with some practice. But shallow depth of field is a little harder to get right.
Polarisers can also see through the reflections on water or glass. Photoshop can't.
$50-$100 for a polariser? Outrageous? Possibly. But at my rates for Photoshop work, that's a bargain.