$100 for all that work is very good price, can't beat that anywhere
as far as flow with port and polish - it makes a lot of difference, now that is relative to what you consider a lot - for example 200cfm vs 220 cfm doesn't seem like a lot but if you're talking VE (volumetric efficiency) that is quite a bit, that 10% is how much more power your engine can make and that's about 12HP for the 4 banger (i'm not saying 220cfm is what our engines are inhaling, just picked that out as an example). and you can actually gain more with a good port and polish job and a good cam. It's painstaking work to get it right though so unless you do it yourself or you have a head that someone wrote a port cnc program for most shops will say they won't do it (comes at a price since there are hours and hours of work). For just a quick surface grind he's right, not much of a difference.