One subtle point about the profit is that because I'm selling a physical product, there are still a lot of unrealized gains in inventory. I estimate that if stopped purchasing new material and just liquidated my existing stock, there'd be about $350k in profit at the end.
That said, I don't think hardware is a good path for a bootstrapped business. I went into this thinking I'd mainly be focusing on selling the software to people who already had the hardware, and then it turned out that there was much more demand for pre-made hardware.
There are many of other tech business paths that are friendlier to bootstrappers, like content businesses, SaaS tools, and educational products. I know of several founders making a comfortable living in those domains, so I wouldn't generalize based on my experience.