“I had PS+ on my previous SD (I'm UK based) and took it for granted. When I changed into a GTS without PS+ I really felt the difference. Retrofit is easy - it is only a coding and software install - and it took my OPC around an hour or so to complete at a cost of £240 - so approximately $300 or so. Big improvement, in my view, and money well spent.”
That was 2019 so I suspect it will be a little pricier now.
UPDATE: and covered on this forum apparently. Sadly I can’t get the link to post. Seems it costs about £300 and takes about an hour