I already said I don't mind the expansion costs. Your post is redundant. The minor DLC is overpriced.
This is the "vote with your wallet" principle at work. Think of DLC not as mandators stuff that you are forced to buy to have fun with your game, but instead as optional extras you can buy if you feel like it - kinda like the extras in cars.
If you don't like the suede seat coverings, the genuine beechwood inlays, the retractable cup holders or the windows that tint at the touch of a button, don't buy them. None of them are needed for the car to do what you buy it to do - in fact, many of those are absolutely worthless for a good amount of potential customers. They're just there for the people that enjoy that kinda thing and that want to spend some extra for a car that has been customised to their liking a bit more.
Same for the small music/cosmetic DLCs for 5 bucks a piece. If you don't place value on customising your army uniforms or having certain themes played as you march into battle or whatever, then that's totally fine. But if you ARE into that stuff, the option is available.
If the prices seem bad for this content, that just means you're not the target audience. Similar to how I am not the target demographic for a 45.000,- Rolex Diamond Titanium with 3 time-zones - I'd rather buy a house and rent it out for that money.
I also often consider soundtracks and visual assets as something positive because what else are artists gonna do? The overwhelming majority of the Utopia content is mechanics - balancing, coding, while all the artist has to do is make a bunch of icons and 1 habitat design per race + generic ring world and dyson sphere construction phases.
So while the coders are busy doing their stuff, the artists make optional cosmetic DLC to justify their paychecks and help balance the budget.