There are quite a few Master's in Development Economics / ID & E that might work as a compromise if your DS is set on doing a Master's.
A problem with Master's in Economics and Business & Finance is that the ones that might, simply by virtue of possession, provide a bit of a wow on a CV for employers who care about that kind of thing are now extortionately expensive, as universities know that part of their value is in getting their name and associated reputation on your CV. To get a UK wow name in Economics or Finance on your CV, unless you get a scholarship you would be looking at course fees of at least £25K-£35K plus all living expenses. That's an awful lot of money to get your DS a Master's he doesn't want to do that might help him get a job in a specific area he doesn't want to work in. It's also not likely to be a very fun experience for him, since most people paying that kind of money really want to be there and really want to do very well.
Outside of the wow names (or just loving the subject and wanting to study it more), I would consider whether the Master's will allow him to develop specific higher level skills and knowledge or experiences that he has not developed on his undergraduate degree and that he has identified as being particularly valuable in seeking the kind of employment he wants to seek. This might be something like higher level quants or research / analytical skills or the ability to specialise to some extent in a particular area of economics or business / finance. Generally, it is the possession of those skills or knowledge that will make the most difference in finding employment, moreso than possession of a Master's degree in and of itself.
If you don't have a reason for doing a Master's beyond that you might as well and can't provide a coherent explanation of what you will get out of it beyond wanting to put an MSc on your CV, you are unlikely to make wise decisions about what to study or, consequently, be able to impress a potential employer with it enough for them to offer you a job when they wouldn't before you did it (professions that just require you to have a Master's aside). It's not even really the case that employers would see having a Master's as singling someone out as particularly clever or dedicated anymore, as it's become increasingly common and spinning your wheels doing a generic and unfocused Master's, often in exactly the same subject as your first degree, is a well-known Plan B for anyone who cares pay for it.
In those circumstances, rather than spending a lot of money doing a Master's that might never be of any benefit to you other than giving you another lovely year at university, you would be better off working for a while (it wouldn't have to be years and years) to allow you to determine whether a Master's would benefit you and, if so, what kind of Master's, in what subject and where. It might turn out that having a Master's is indeed beneficial in itself, it might turn out that a more specialised Master's would be more beneficial, or an MBA, or only an MSc from certain places, or some kind of non-Master's training. You can then do one of these things based on the specific knowledge you have of what will actually help your career rather than just vaguely hoping that unspecified employers will in some way value something to some unknown extent which, in your DS's case, he doesn't see the value in himself because he can't see how it would help him to do what he wants to do.