Apparently naively, I would have expected BoM to be markedly more predictable, and controllable, than either legal or software costs.
No, it is in the real world of buying stuff, doing something to it and selling it for a profit that the real risks and rewards of business lie.
Legal and software costs are generally annoyances rather than the cause of businesses going bust, whatever the hysteria on places like slashdot.
The tl;dr here is that Triggertrap didn't have a properly costed business plan. Like most failed businesses.