A few comments.
2. Look at the price tag. Analog discovery is USD $200+ to USD $1000+. This one should not exceed USD $70.
Totally unrealistic, manufacturing this in hundreds will cost something around $50-70 for you (components, PCB + assembly). If you want to cover any R&D, support, marketing, bare minimum selling price will be around $200.
3. I don't understand the hate on the RS-232.
(emphasis mine)
And I don't understand why anyone would hate horses, and a horse carriage in 1890 was a totally viable product, but if you tried to produce cars which lack engine and require adding an external horse in 2022, you can see why no one wants to buy it, yes?
Especially if the target group is students and hobbyists, look why Arduino was popular: the USB port, and this was already over a decade ago.
In other words, computers you connect to have USB ports, they don't have RS232 ports no matter how much you like it. Hence, your product must have an USB port, too. Basically just remove unnecessary level translators (cost savings!) and then integrate the USB-serial chip on-board, look at Arduino for implementation example. Job done.
- The entire device is designed with through hole components.
Why on the Earth would you do that, and even worse, IC sockets!? What the heck are you thinking? Again the horse thing: the whole electronic manufacturing went SMD 25-30 years ago. This ancient TH DIP IC technology node not only greatly limits your choice of components, it also blows the production costs through the roof (making yout $70 price target even more unrealistic).
You literally demonstrate right here the problem: you can't make the product work stand-alone because you can't find the necessary modern day IC you would need, because the arbitrary through hole limitation.
SMD design allows automated manufacturing. Chinese will of course wave solder (or hand solder) TH parts for you, too, but SMD gives you smaller board size, meaning further cost savings.
If the device is sold as DIY with user solders the parts
So will it? You have to decide if this is a "learn to solder" DIY kit, or an instrument. The web page gives an impression this is a pre-assembled instrument (it even states clearly: "category: lab equipment"), not a kit. Note that DIY kits are a completely different business segment. Trying to satisfy both kit customers and those who want an affordable pre-made instrument, at once, is colossally difficult. What you can opt for is to leave the user to hand-solder the few through hole parts (like pin headers).
- If the user wants to use the Terminus with any of their own project, they can interface directly via UART. It is way easier than interfacing with USB. The device has both direct connection for USB-UART and a onboard level convertor. The user uses what they want.
I agree with that and nothing prevents you from exposing the UART interface to the user.