I've recently read about that, partly because I have degrees in economics. I have found the following article on it, despite being a bit dated:
https://www.businessinsider.com/emolument-humanities-phd-cost-2016-5?r=US&IR=TMost of the salaries mentioned on there don't seem realistic for the UK, and if they are, a good chunk will go towards tax.
There was a particular article that attributes most of the large salary differences to people working in banking and finance (or the big 4 accounting firms), and I find this to be mostly true. Having said that, living in the City isn't cheap either, so you will need the high salary to live OK (I wouldn't try anything less than £20k, otherwise you may struggle).
I then looked at economist jobs with the government, and they don't particularly pay a lot (£40k after 3 years training), so if you stand to get the £50-60K range, you will need to get promoted. The entry level jobs aren't easy to get anyway; I've spoke to a Manchester graduate with a first class degree in Economics who failed to secure a job as an economist because of the level of competition.
There are jobs with NGOs and think tanks, but getting a job with them isn't easy, especially not the one you want to work for. Also, most will be asking for PhD in economics.
I haven't really found many economist jobs in the private industry without asking for years of experience beforehand. They're not particularly easy to get, and I can only see big companies asking for those people.
The general rule of thumb I find is the higher the pay, the more competition and office politics you expect there to be, irrespective of the profession. That's not easy to handle. Getting promoted when competition is fierce and the number of suitable candidates is high is particularly difficult to deal with, especially when you're working in an organisation with a flat structure. Getting into academia is also difficult, and people are working for barely anything at all.
I suppose when you come down to it, research in economics is particularly important when it deals with the economic prosperity of the country. However, that prosperity needs to reap in thousands-millions of times what you are being paid, so you will have to be really good i.e. there is no reason for someone to pay you if you don't reap the returns (same with other high paying jobs - why should they pay you £X?). Having said that, most of what economists do is trying to fit trends and models onto data and to do talks on it, as far as I know.
Having done the degrees, I'd say you don't need to know a lot of maths, since I don't think you will need to know anything beyond AS Level. The main things you might need to be aware of is you need to understand hypothesis testing (statistics) for econometrics, and maybe differentiation for microeconomics and a bit of macroeconomics. The other maths you might come across doesn't go higher than GCSE. Unless you try to hype it up and go into mathematical economics (or do a module in it), I'd doubt you need to know that much maths.
Most of economics is in regards to discussing theories. A good introductory book on it is Mankiw's Principles of Macroeconomics - a book I recommend most people buying, irrespective of whether they do an economics degree or not.