Typically, I like to auto-gen each distinct price value into a dimension and then build a slider on top of that dimension with a histogram.
So across your entire product catalog, you might see a dimension called Price look like this:
Then, as your users refine by other dimensions, the price dimension (or in this case the slider with histogram) recalcutes.
It certainly could be if the list of distinct price points has high cardinality. It is something to look out for. The performance impact is going to be in the size of the response required to generate the histogram. Typically, we try to keep the entire response size < 50K for any portlet.