The term "polishing" I think is miss qouted, you do not increase flow with mirror polished chambers or ports. You need a nice texture in the port area, porting can mean anything from one place to another. In terms of what we do here to another is going to vary, as will price. Hard to beat having your heads ported. I have seen the low prices on SE heads, you may want to go with that. Will they flow more than a set done by a good porter no but then again if you cannot locate one then that might be the way to go.
Cost on porting is all over the place, I would have to say that talking with the porter is the first step, how is the service done?? What steps do they take, What parts are re-used, what parts are new, brand of new part, do they set seat PSI for your cam, do they swap springs?? If new springs what is the seat PSI?? I have seen heads that had great port work with new springs. I checked the seat psi and I know what the spring is advertised to be at but this spring pack was at 195 on the seat!! That is a ton of PSI for a mild cam. That is wasted HP there not to mention that valve train noise would most likely happed. Hope I was some help