"As we discussed earlier, even at $300 the product is too cheap. The sign should have likely been selling at $600 from the very beginning."
Even at $600 - there's a screenshot saying the company had three engineers and a marketer.
If your 4 employees earn $25k per annum, with the $150 parts cost you'd have to sell 222 signs at $600. And if the employees were on $100k, that's 888 signs a year.
That's a heck of a lot of signs, at the price. And you'd have to keep hitting those sales targets so long as you wanted the API to stay up.
It would make much more sense if the business was a one-engineer passion project - someone who had a day job and did a few hours a week maintaining this as a side project would have much more achievable sales targets!