I agree with the previous post, whereby how successful or how much you can earn can only be say once you actually reach there (success). It does not mean you work hard or have more years of experience will equal to higher pay. It depends on your company whether it offers a good career path, depends on your network, luck too if you manage to secure a high paying position in other company before you jump ship. Hence, I really cannot say how high Marketing or Finance career can earn.

To address your other questions,
1) Good Hons is good to have. Some companies really will just filter out those without 2nd upper or above. While some other may consider those without good hons. In your final year, when you applying, companies will see your results and analyse whether you will be expecting at least 2nd upper or not. Even if no, they might also interview you first. Hence, don't worry, not all companies will just disregard if you don't hit the minimum requirement. But good hons is one of the factor to make you more 'recognisable' out of their large pile of resumes.

2) Earning power and career progression. I think the previous post mentioned this very well. Even if you have first class hons, if you cannot secure a good job, when you apply for 'low tier' companies your salary will be in the range of those basic degree without hons, because these companies can only offer that much and they don't have so many resumes so don't need to lessen it down to a few applicants, thus don't really look for good hons. And career progression largely depend on what you do when you starts working. Whether does the company offers a good career progression? Otherwise, after 1-3years of experiences, are you able to jump to a higher pay company? Thus, from another point of view, even without good grades, you can still earn a lot.

3) What industries pay graduates well? Be it marketing or finance degree, companies that are looking for good graduates, and have the financial capabilities, they would be willing to pay these graduates well. All kinds of industries do seek out for good graduates, even marketing. You can try searching for "Singapore’s 100 Leading Graduate Employers". Most of them pay graduates well. BUT, do remember these are also the popular companies everyone is applying for. So you really need to stand out. Like I mentioned, there are also online tests/ assessment center and stuff to really find those good graduates. Usually those that pay well will be a MNC, and have some graduate programs/ management associate programs.

== All in all, I understand that you want to make the right choice, and concern about the salary and career progression. But I will say don't just keep thinking or analysing what is the right choice. Take on a more active approach, like applying for case competition from those companies you are interested in, ask from your senior about the companies recruiting process, and learn to excel in it. Like I said, even if you are able to find the right choice and your dream job, it does not mean you can secure it. There are many many other graduates, who may have better resume/ skills to do will in interviews/ assessment center. There is no 'right' choice, and doesn't mean your first job equal to lifetime job. I will advise set 2-3 companies as targets, take up their case competitions/ attend their career fairs to network, and ask your seniors who are applying for these companies the application process and learn from them if the pass or fail. If grades are not your forte, then you have to find ways to stand out compare to the rest. And these are some of the ways.