Great questions. The target audience for these instruments are scientists and hobbyists who don't want to spend a ton of money on similar commercial systems, and want the flexibility to modify their operation (e.g., poseidon can run custom flow profiles per experiment whereas off-the-shelf commercial systems typically only run one flow rate per experiment). The purpose of poseidon is to show that open source biological instruments can be developed and used by a community, similarly to how open source software tools in biology are developed and used.
Academic budgets vary from institution to institution and are sometimes determined by exogenous forces beyond the lab's control.
A complete commercial system to do single-cell RNA sequencing costs tens of thousands of dollars! Using alternatives such as the Harvard Apparatus syringe pumps and DropSeq [0] to run the same experiment will still cost you into the thousands of dollars. With the poseidon system, we greatly reduce these costs. Users can build the instruments to run these experiments for less than $400 and are not restricted to additional costs and tedious firmware upgrades to expand the system.
In response to your point on time management and instrument-making, I think that if there exists a need to develop these systems such that they will advance biological experiments then it's totally cool to have academics work on these sorts of projects! Biologists and bioengineers have always developed tools alongside discovery and this is no different from developing bioinformatics tools.
The poseidon system was explicitly designed with ease of assembly in mind. If you look at the build videos [1] you'll see that assembly of the entire system (3 pumps + microscope station) takes less than an hour and requires just pliers and screwdrivers.
The importance of ease of assembly was a lesson that we took from assembling the miniDrops microfluidics station [2] developed specifically for one kind of experiment (dropSeq) [3]. The miniDrops is very good at what it does but assembly was somewhat cumbersome: it required ordering a custom PCB, specialized parts only available from one vendor (whom I had to nag over the phone to send me a quote!) and assembly of the device itself took 10-20h.
Not every kind of equipment can be made as easy to source and assemble as we did with poseidon, but we really think that keeping this at the front of your mind can make or break the adoption of a piece of open source hardware. This is especially true in the context of biology laboratories, where many people are not what you could call "hackers" or "makers" and will be immediately put off by a daunting assembly process.
[1] https://pachterlab.github.io/poseidon/hardware
Additionally, in my lab and many others, there simply wasn't any tool we could use to answer all the questions we have, so we had to invent them. That said, these are much more bespoke systems, but as we push the envelope of what we need to observe, instrument making and method development are only going to be more critical.
The inflation in the scientific equipment market is also ludicrous. Since I've been in grad school some of the things I have to buy have doubled in price. And it really is pathetic when it's something like a syringe pump - I mean you're rotating a screw with an electric motor to push a piece of plastic. I get that it's a small market and the vendor has to make a living, but this isn't the best way for a civilization to direct its resources.
sobs
This is an age old question. And the answer is: yes, we actually do.
Even if a lab can afford all its instruments, sometimes you are researching something that requires a different approach. Most commercially available lab machines are NOT hackable, and you will have a difficult time bending them into a different configuration.
And a lot of the time that equipment isn't funded by a current project and you need to prove the idea is sound before you can justify asking for the money to do it. Of course if that proof of concept is good enough to keep being used all the better.