I was thinking about the case itself, not the components, but good thing you brought it up, it is indeed an issue with other cases of this layout.
Ah I didn't know we were talking about GBP here, that seems a little more achievable. I think that price is absolutely fine, indie SFF cases are even more expensive most of the time, so I think you're aiming for the right spot.
With shipping there's always the issue of the dimensions of the case and you can try to design it in a way that it's even smaller disassembled, but I don't know whether that will help. The prices seem ok to me, but maybe there is a shipping service for the US that takes longer but is less costly?
Well, that's a very good and controversial question, and I think you'll have to put up a poll once your case has gotten enough attention to find out.
A lot of people will argue that front I/O makes the case uglier, some think Audio is completely unnecessary, others don't want any of it. As your sales volume is going to be very low, you could try to put the cutouts for the I/O on the side where it doesn't hurt the aesthetic too much and just include the actual I/O board as an option.
That way people could choose whether they deem it worth it or not.
For my case I'm exploring the route of hiding the I/O and making it upgradable, but that requires designing the I/O circuitry yourself and complicates the design significantly.
