PB does make valid points and really is up to you if you'll see value there. Price wise, I suppose it depends on what he's quoting for the entire system but is probably in line (there are likely other folks here who could give a more definitive answer if that's a good price). My system was upgraded for free (FW update) due to my PB basically owing me for a couple of massive issues along the way.
But that said - me personally, I use it all the time and wouldn't have it any other way, especially after experiencing the PDA version for a few weeks. I'm geeky like that and may check on things once a day (or every other). If I had just the PDA system running, I likely wouldn't be as in tune with my pool as I am today b/c the range, interface and speed is just not a good experience. The biggest thing for me is that I'm able to retrieve all equipment status and feedback from my phone - i.e. pump wattage, salt cell output, salt level, system errors, etc. Being a SWG pool, the ability to adjust and monitor output from my phone anywhere is great and was one of the first things I asked for when we planned the build (PB designer didn't understand the ins/outs as much which is why they STILL initially sold me the PDA system).
With the PDA + iAqualink system, there is no way to view salt output, salinity, pump wattage, system errors, vsp adjustments, etc. without doing it locally on the PDA screen. In other words all you can do from your phone is turn pumps on/off, light colors, spa mode, cleaner (if applicable) and heat adjustments. For most people that's probably all they really need in all honesty.
Another way to look at it is if you lose your PDA or is broken, you can't program your system without a replacement Jandy PDA as far as I know. With RS, you can use any phone(s), etc. If you search some threads here about iAqualink, you'll find lots of folks questioning why they can't do certain things as they come to the realization they have a PDA system and they usually go through great lengths to move to RS by swapping out boards, etc. just to get to that point. IMHO for $820 you have full access to your system w/out the annoyances of the PDA and is totally worth it.
All that said - even the RS system is a bit antiquated from a UI design perspective so don't expect miracles (it's basically a web app hosted in the normal iaqualink app) - but it's way better than just the PDA. I think it would be best if your PB could show you both systems as they work so you can make personal decision on it. $820 is a lot of money and whether or not you get value out of it is going to vary per person.