The Razer Core is not designed to expand I/O. It's designed to improve graphics performance on laptops, and more specifically it's designed to improve gaming performance. Nobody's putting anything other than a graphics card in this, the markets are different (Magma for pros vs Core for consumers), etc.
Also, your own use cases are hardly "consumer"-oriented, but I'll get to that in a moment.
Sure. That's why I said this:
So we aren't disagreeing there. If all you care about is exclusively using a laptop, and specifically don't want multiple systems, and specifically want to maximize performance only when at your desk, and you're specifically targeting a professional use case that isn't gaming, and you specifically are willing to pay any price... then this is probably your only real choice. But that's a subgroup of a subgroup of a subgroup of a subgroup of a subgroup of people.
Most people who see this will exist outside of that group. Most people will just want better gaming performance. Most people fall under that broad "casual use and gaming" bucket you called out. And, thus, my point is that most people are better served by building a desktop.
No, I don't have to do that. I just have to demonstrate that I can create a substitute that does the same or better job, for as much or for less money. Outside of the highly specific exception I stated above, I have demonstrated that people who want to use the Core to improve gaming performance (which is what the preponderance of Razer's own promotion specifically calls out) are financially better off just building an entirely new system - which, you'd agree, provides exceptionally more utility for that majority of use cases than the Core.
Put it this way: I live in Boston, and although you can't "directly compare" the T (our subway system) to a sedan, guess what - the T is better at what the car does for the majority of people. To that majority, the car is overpriced for what it provides.
I think you're overstating the effort of setting up software - which you should only ever have to do once, I'd imagine? - but we can just agree to disagree there. I don't have experience in 3D modeling/rendering, either, so I won't claim that I know that struggle 
Still, anything is arguable with the caveat of "at any cost", so that's not really a good argument in support of doing something. At that point, the discussion is no longer about value, because you've removed the constraint of cost, and that's all that I'm talking about here - that, for the vast majority of enthusiasts, this product is a terrible value. Most people considering this would be better off building a system.
By that logic, a $500 rock isn't overpriced in a market that only has $2500 rocks. That's just silly.
Something is overpriced not as a function of other prices for the same thing, but as a function of the utility it delivers in comparison to a reasonable substitute. For most people, an entirely new system is a reasonable substitute, and the Core compares terribly to that.
Maybe that doesn't include you, but we're not talking about you, we're talking about the "consumer" - your average enthusiast. Who can't afford things "at any cost", and isn't doing 3D modeling, and mostly wants to have the best gaming performance possible for the money.
...Anyways, for the most part, I don't think we really disagree. This can be a fantastic value for you, given your needs and workflow, and that's all that matters for you. All I was trying to say - though I probably wasn't direct or clear enough - is that I feel that this is a terrible value for almost anyone else, and especially for the population that Razer itself is targeting, which is laptop-toting gamers.
