Does it make sense to get a PhD if a person does not want to be in academia and prefers to stay in business? I am working in a highly technical field (quantitative finance/ statistical analysis) for a private company with a Master of Science degree in economics. 

Does it make sense to get a PhD (in quantitative finance, math, statistics) if I do not want to be in academia and prefer to stay in business.  

What I expect from PhD: 


Structure and deepen my knowledge in the relevant fields through
high quality classes (where I sit and listen and learn and do
homework to make sure that I have learned).
Get the ability to read any scientific article in the related fields and without much pain understand 90% of it to the very last detail (and implement ideas from the article in my work).
Possibly acquire certain thinking and problem solving culture (so vague... and I guess after my Master I have a fair part of it already(?))   


Also important:


PhD was never mentioned as a prerequisite for a promotion or a salary increase. 
My colleges who have PhD are not visibly advantaged by the company (do not know about the rest of the industry, but the company being a big player is representative of it).
I enjoy learning new stuff on my own (not a problem to spend many nights with a math book), but hate the status of a student (little money, slave of professors and their peculiar exam requirements). 


So should I go for a PhD or rather a specialized Master, or develop myself through separate university courses of my choice and professional programs + self-study? 

Any pieces of advice from people used to be in my situation?
Ultimately no one else can make this decision for you. At best we can give our biased (after all many of us here will have taken the PhD/academic route) opinions.

First of all doing a PhD for financial or career reasons is not, in general, a good idea. Yes we all know the story of google, but Larry Page and Sergey Brin didn't go into the PhD planning to make it big and it was their passion that produced google. A PhD is a long and sometimes painful process taken on because the individual gets a buzz from the challenge, the field and a desire to push it forward. There will be weeks if not months when nothing is working or making sense. I think it was Boot and Randall, after having developed the high-power magnetron for radar at Birmingham university and giving the allies a much needed early warning system, who attributed their success to something akin to "the one day in which all the equipment in the lab happen to work". Tongue and cheek and modesty no doubt, but it serves as a good antidote to research life - very few things, codes included, work first time! Its the burning passion that keeps you going time and time again until you get results. 

Second, a PhD is not taught (Not sure where your from but the USA and some European PhD's do have a taught masters in the first year, but this is not the norm in Europe). Classes to a large extent are not an efficient use of time, they serve to give a broader overview of the field but will certainly not be anywhere near enough to get you through a PhD. If its being taught in a class its not research! And its certainly not going to be a novel idea for your thesis. At the end of the PhD you should be the world expert on the niche area of your field, there are no (or few) textbooks on the subject - because you have written them yet!

When reading papers, even the most experienced academics, are unlikely to understand everything first read, the specific technique maybe, the unique application? probably not. As a research you don’t want to waste time absorbing every little detail, just the bits relevant to your research. You simply don’t have time.

Research does teach you a certain set of skills, first is how to deal with failure and keep going - Persistence. Project management (3 year long project after all) skills and of course critical thinking and problem solving skills, particularly in the  technical areas.

Now, none of what I said should be taken as trying to put you off but rather help you make an informed decision. You could possibly look at a research masters, known as an MRes? This may be the best of both worlds. Good luck with whatever you choose to do and remember you don't need PhD's or degrees to continue learning, someone above mentioned online course and these open access avenues are a great way to expand your knowledge.