Possibly outing myself, but I worked for an investment bank on quite a comfortable salary (they claimed to pay the national average + 10% for professional roles - clerical roles were local average + 10%.) Started as a graduate trainee, and was there a few years, including over Y2K and the dot com boom, which did have a positive effect on salaries at the time, and after the dot com crash, they did take a hit in many places, and payrises/bonuses weren't so generous.
I left to take some time out travelling, then came back and failed to find a job so easily. Ended up working for the public sector doing exactly the same role, but on 50% of the salary, so let's say £20K when I had been on £40K - though still better than the minimum wage I was on on temping, and that was better than having to turn up at the job centre and try and survive on JSA.
A year later, I went back to a multinational, not banking (same role again), and got a 50% rise on the public salary (so 75% of the banking one, about £30K.) I could have probably got more if I'd been less naive about negotiating starting salaries, and talked about banking salary more. However, in the banking and multinational, there are also annual bonuses, private health cover and some other benefits, so the overall package is more just the salary. Also, one of the things I really like about my current job is that I get to talk to people all round the world every day, which just didn't happen in the public sector job, and it's a more dynamic atmosphere, too - it's not just about the money for me, though frankly, if I can get quite a lot more money for the same role, then that is going to go against the lower paid one. I also didn't find the public sector job particularly enlightened about equality and diversity, at least in the techy departments, either, which rather surprised me, but I wouldn't like to say that it will be the same in all public sector IT roles, given the range of organisations that covers. (In fact, I don't really like public sector vs private sector debates for that reason anyway - there are too many different types of employer under both public sector and private sector; it makes more sense to compare company sizes and so on.)